Have you ever been in a conversation where someone says, “He’s not the brightest bulb in the box,” and you wonder what exactly that means? Idioms like this are common in English, adding colour and humour to everyday speech. However, they can sometimes be confusing, especially for non-native speakers.
Idioms are phrases where the meaning isn’t obvious from the individual words—they often express ideas creatively or figuratively. This article focuses on idioms related to being “stupid” or not very intelligent, a topic full of funny and memorable expressions.
You’ll find 52 idioms here, each explained with clear meanings and example sentences. To help you learn, there are also exercises and a quiz so you can practice and remember these idioms easily. Let’s dive in and have some fun with these quirky English expressions!
52 Idioms for Stupid
1. Not the brightest bulb in the box
Meaning:
Someone who is not very intelligent or quick-witted.
In a Sentence:
Example 1: He tried to fix the computer by hitting it, but he’s not the brightest bulb in the box.
Example 2: She forgot her keys again—definitely not the brightest bulb in the box.
Other ways to say it:
Not the sharpest tool in the shed, lights are on but nobody’s home, slow on the uptake.
2. Not the sharpest tool in the shed
Meaning:
A person who is not very smart or quick to understand things.
In a Sentence:
Example 1: John missed the obvious answer; he’s not the sharpest tool in the shed.
Example 2: Don’t expect him to get it right the first time—he’s not the sharpest tool in the shed.
Other ways to say it:
Not the brightest bulb in the box, thick as a brick, a few sandwiches short of a picnic.
3. Lights are on, but nobody’s home
Meaning:
Someone appears to be mentally absent or not thinking clearly.
In a Sentence:
Example 1: When she was asked about the meeting, her blank stare showed the lights were on, but nobody’s home.
Example 2: Sometimes during class, it feels like the lights are on, but nobody’s home with him.
Other ways to say it:
Not playing with a full deck, missing a few marbles, out to lunch.
4. Dumber than a box of rocks
Meaning:
Extremely unintelligent.
In a Sentence:
Example 1: Trying to explain the instructions to him was pointless; he’s dumber than a box of rocks.
Example 2: That idea is dumber than a box of rocks and won’t work.
Other ways to say it:
Dumber than a bag of hammers, as smart as a bag of rocks, thick-headed.
5. Thick as a brick
Meaning:
Very stupid or slow to understand.
In a Sentence:
Example 1: He’s as thick as a brick; I had to explain the concept three times.
Example 2: Don’t bother arguing with him—he’s thick as a brick.
Other ways to say it:
Thick-headed, not the sharpest tool in the shed, slow on the uptake.
6. He’s got a screw loose
Meaning:
Someone who behaves strangely or is mentally unstable.
In a Sentence:
Example 1: He talks to himself all the time; I think he’s got a screw loose.
Example 2: Don’t trust him with the plan; he’s got a screw loose.
Other ways to say it:
Has a one-way ticket on the crazy train, bats in the belfry, out to lunch.
7. Slow on the uptake
Meaning:
Slow to understand or grasp something.
In a Sentence:
Example 1: She’s a bit slow on the uptake, so be patient when explaining.
Example 2: He’s slow on the uptake, which is why he missed the joke.
Other ways to say it:
Not the brightest bulb in the box, thick as two short planks, not the sharpest tool in the shed.
8. A few sandwiches short of a picnic
Meaning:
Not very intelligent; missing something mentally.
In a Sentence:
Example 1: He’s a few sandwiches short of a picnic if he thinks that will work.
Example 2: Don’t take him seriously—he’s a few sandwiches short of a picnic.
Other ways to say it:
A few cards short of a full deck, missing a few marbles, not playing with a full deck.
9. All brawn and no brains
Meaning:
Strong but not intelligent.
In a Sentence:
Example 1: He can lift heavy weights but can’t solve simple problems—he’s all brawn and no brains.
Example 2: The new recruit is all brawn and no brains, so he needs help with strategy.
Other ways to say it:
Meathead, bonehead, thick-headed.
10. Thick-headed
Meaning:
Difficult to understand or slow to learn.
In a Sentence:
Example 1: I explained it twice, but he’s thick-headed and still didn’t get it.
Example 2: She’s too thick-headed to realize her mistake.
Other ways to say it:
Thick as a brick, not the sharpest tool in the shed, slow on the uptake.
11. Not playing with a full deck
Meaning:
Someone who is mentally deficient or not fully sane.
In a Sentence:
Example 1: He’s not playing with a full deck if he thinks that’s a good idea.
Example 2: After the accident, people said he wasn’t playing with a full deck anymore.
Other ways to say it:
A few cards short of a full deck, missing a few marbles, not the sharpest knife in the drawer.
12. A few beers short of a six-pack
Meaning:
Mentally slow or lacking intelligence.
In a Sentence:
Example 1: He’s a few beers short of a six-pack if he thinks he can finish that project alone.
Example 2: Don’t expect him to understand—he’s a few beers short of a six-pack.
Other ways to say it:
A few sandwiches short of a picnic, not playing with a full deck, missing a few marbles.
13. Mad as a hatter
Meaning:
Completely crazy or insane.
In a Sentence:
Example 1: His wild ideas make him seem mad as a hatter.
Example 2: She’s mad as a hatter, talking to herself in public.
Other ways to say it:
Bats in the belfry, has a one-way ticket on the crazy train, got a screw loose.
14. As sharp as a marble
Meaning:
Very unintelligent or slow-witted.
In a Sentence:
Example 1: He’s as sharp as a marble and can’t follow simple instructions.
Example 2: Don’t ask him for advice; he’s as sharp as a marble.
Other ways to say it:
Not the sharpest tool in the shed, not the brightest bulb in the box, thick-headed.
15. He doesn’t have both oars in the water
Meaning:
Mentally unstable or not thinking clearly.
In a Sentence:
Example 1: That guy doesn’t have both oars in the water; he’s always acting strangely.
Example 2: If he doesn’t have both oars in the water, he won’t be able to handle this job.
Other ways to say it:
Not playing with a full deck, missing a few marbles, out to lunch.
16. Missing a few marbles
Meaning:
Mentally deficient or crazy.
In a Sentence:
Example 1: She’s missing a few marbles if she thinks that plan will work.
Example 2: After the accident, people said he was missing a few marbles.
Other ways to say it:
A few cards short of a full deck, not playing with a full deck, a few sandwiches short of a picnic.
17. A few cards short of a full deck
Meaning:
Not mentally sound or lacking intelligence.
In a Sentence:
Example 1: He’s a few cards short of a full deck, so don’t trust his judgment.
Example 2: That idea is crazy—he’s a few cards short of a full deck.
Other ways to say it:
Not playing with a full deck, missing a few marbles, a few sandwiches short of a picnic.
18. Bonehead
Meaning:
A stupid person.
In a Sentence:
Example 1: Don’t be such a bonehead; think before you act.
Example 2: Only a bonehead would forget their own birthday.
Other ways to say it:
Meathead, thick-headed, not the sharpest tool in the shed.
19. Out to lunch
Meaning:
Absent-minded or not paying attention.
In a Sentence:
Example 1: He was out to lunch during the meeting and missed all the important points.
Example 2: Sometimes she seems out to lunch and doesn’t understand what’s going on.
Other ways to say it:
Lights are on but nobody’s home, not playing with a full deck, bats in the belfry.
20. Not the sharpest knife in the drawer
Meaning:
Not very intelligent.
In a Sentence:
Example 1: He’s not the sharpest knife in the drawer, but he tries hard.
Example 2: That comment showed she’s not the sharpest knife in the drawer.
Other ways to say it:
Not the brightest bulb in the box, not the sharpest tool in the shed, as sharp as a marble.
21. The wheel is spinning, but the hamster is dead
Meaning:
Someone who appears to be thinking but isn’t actually processing anything.
In a Sentence:
Example 1: He keeps talking nonsense; the wheel is spinning, but the hamster is dead.
Example 2: Don’t expect him to solve the problem—the wheel is spinning, but the hamster is dead.
Other ways to say it:
Lights are on but nobody’s home, out to lunch, not playing with a full deck.
22. Elevator doesn’t go all the way to the top
Meaning:
Mentally slow or not fully intelligent.
In a Sentence:
Example 1: He’s a nice guy, but the elevator doesn’t go all the way to the top.
Example 2: Sometimes I wonder if the elevator goes all the way to the top with her.
Other ways to say it:
Not the sharpest tool in the shed, thick-headed, slow on the uptake.
23. A few bricks short of a load
Meaning:
Mentally deficient or crazy.
In a Sentence:
Example 1: That plan is crazy—he’s a few bricks short of a load.
Example 2: Don’t trust him with important tasks; he’s a few bricks short of a load.
Other ways to say it:
A few cards short of a full deck, missing a few marbles, not playing with a full deck.
24. A few fries short of a Happy Meal
Meaning:
Not very intelligent or mentally deficient.
In a Sentence:
Example 1: He’s a few fries short of a Happy Meal, but he’s a good guy.
Example 2: That idea is silly—he’s a few fries short of a Happy Meal.
Other ways to say it:
A few sandwiches short of a picnic, not playing with a full deck, missing a few marbles.
25. Fell out of the stupid tree and hit every branch on the way down
Meaning:
Extremely stupid.
In a Sentence:
Example 1: Only someone who fell out of the stupid tree and hit every branch would do that.
Example 2: He’s so clueless, it’s like he fell out of the stupid tree and hit every branch on the way down.
Other ways to say it:
Dumber than a box of rocks, bonehead, thick-headed.
26. His cheese has slipped off his cracker
Meaning:
He’s acting crazy or irrational.
In a Sentence:
Example 1: Ever since the accident, his cheese has slipped off his cracker.
Example 2: Don’t listen to him; his cheese has slipped off his cracker.
Other ways to say it:
Got a screw loose, bats in the belfry, mad as a hatter.
27. A village is missing its idiot
Meaning:
A sarcastic way to say someone is very stupid.
In a Sentence:
Example 1: When he left, it was like the village was missing its idiot.
Example 2: That comment made it clear he’s the village idiot.
Other ways to say it:
Bonehead, thick-headed, not the sharpest tool in the shed.
28. Dumber than a bag of hammers
Meaning:
Extremely unintelligent.
In a Sentence:
Example 1: He’s dumber than a bag of hammers if he thinks that will work.
Example 2: That idea is dumber than a bag of hammers.
Other ways to say it:
Dumber than a box of rocks, thick-headed, bonehead.
29. He couldn’t pour water out of a boot with instructions on the heel
Meaning:
Very incompetent or unintelligent.
In a Sentence:
Example 1: He couldn’t pour water out of a boot with instructions on the heel—he’s hopeless.
Example 2: If you give him directions, he still can’t figure it out; he couldn’t pour water out of a boot with instructions on the heel.
Other ways to say it:
Not the sharpest tool in the shed, bonehead, thick-headed.
30. Meathead
Meaning:
A person who is strong but not intelligent.
In a Sentence:
Example 1: He’s a meathead who spends all day at the gym but can’t solve simple problems.
Example 2: Don’t expect much from him academically; he’s a meathead.
Other ways to say it:
All brawn and no brains, bonehead, thick-headed.
31. If brains were dynamite, he wouldn’t have enough to blow his nose
Meaning:
Extremely unintelligent.
In a Sentence:
Example 1: If brains were dynamite, he wouldn’t have enough to blow his nose.
Example 2: That guy is so dumb, if brains were dynamite, he wouldn’t have enough to blow his nose.
Other ways to say it:
Dumber than a box of rocks, thick-headed, bonehead.
32. As smart as a bag of rocks
Meaning:
Very unintelligent.
In a Sentence:
Example 1: She’s as smart as a bag of rocks when it comes to math.
Example 2: Don’t expect him to understand; he’s as smart as a bag of rocks.
Other ways to say it:
Dumber than a box of rocks, thick-headed, not the sharpest tool in the shed.
33. Not the sharpest crayon in the box
Meaning:
Not very intelligent.
In a Sentence:
Example 1: She’s not the sharpest crayon in the box, but she tries her best.
Example 2: That answer shows he’s not the sharpest crayon in the box.
Other ways to say it:
Not the brightest bulb in the box, not the sharpest tool in the shed, as sharp as a marble.
34. A few clowns short of a circus
Meaning:
Mentally deficient or crazy.
In a Sentence:
Example 1: He’s a few clowns short of a circus, so don’t take him seriously.
Example 2: That plan is crazy—he’s a few clowns short of a circus.
Other ways to say it:
A few cards short of a full deck, missing a few marbles, not playing with a full deck.
35. Bats in the belfry
Meaning:
Crazy or mentally unstable.
In a Sentence:
Example 1: She’s got bats in the belfry if she thinks that’s a good idea.
Example 2: Don’t mind him, he’s got bats in the belfry.
Other ways to say it:
Mad as a hatter, got a screw loose, has a one-way ticket on the crazy train.
36. Chucklehead
Meaning:
A foolish or stupid person.
In a Sentence:
Example 1: Only a chucklehead would forget to lock the door.
Example 2: Don’t be a chucklehead—think before you act.
Other ways to say it:
Bonehead, meathead, thick-headed.
37. Dumber than a box of hair
Meaning:
Extremely unintelligent.
In a Sentence:
Example 1: That suggestion was dumber than a box of hair.
Example 2: He’s dumber than a box of hair when it comes to technology.
Other ways to say it:
Dumber than a box of rocks, thick-headed, bonehead.
38. Forgot to pay his brain bill
Meaning:
Not thinking clearly or acting stupidly.
In a Sentence:
Example 1: He must have forgot to pay his brain bill to say something like that.
Example 2: Don’t listen to him; he forgot to pay his brain bill.
Other ways to say it:
Lights are on but nobody’s home, out to lunch, not playing with a full deck.
39. If he had another brain, it would be lonely
Meaning:
Very unintelligent.
In a Sentence:
Example 1: He’s so dumb, if he had another brain, it would be lonely.
Example 2: That idea shows if he had another brain, it would be lonely.
Other ways to say it:
Dumber than a box of rocks, thick-headed, bonehead.
40. Not the sharpest tack on the board
Meaning:
Not very smart.
In a Sentence:
Example 1: She’s not the sharpest tack on the board, but she’s a hard worker.
Example 2: That mistake shows he’s not the sharpest tack on the board.
Other ways to say it:
Not the brightest bulb in the box, not the sharpest tool in the shed, as sharp as a marble.
41. As much use as a chocolate teapot
Meaning:
Completely useless or ineffective.
In a Sentence:
Example 1: That old computer is as much use as a chocolate teapot.
Example 2: His advice was as much use as a chocolate teapot in a rainstorm.
Other ways to say it:
Not the sharpest tool in the shed, all brawn and no brains, bonehead.
42. As thick as two short planks
Meaning:
Very stupid or slow to understand.
In a Sentence:
Example 1: He’s as thick as two short planks and can’t follow simple instructions.
Example 2: Don’t bother explaining; she’s as thick as two short planks.
Other ways to say it:
Thick as a brick, thick-headed, not the sharpest tool in the shed.
43. Has a one-way ticket on the crazy train
Meaning:
Mentally unstable or crazy.
In a Sentence:
Example 1: After that weird rant, it’s clear he has a one-way ticket on the crazy train.
Example 2: Don’t trust his judgment; he has a one-way ticket on the crazy train.
Other ways to say it:
Got a screw loose, bats in the belfry, mad as a hatter.
44. Mind of a child
Meaning:
Simple-minded or naive.
In a Sentence:
Example 1: He has the mind of a child when it comes to understanding complex issues.
Example 2: She approaches problems with the mind of a child, which sometimes causes trouble.
Other ways to say it:
Not the sharpest tool in the shed, slow on the uptake, out to lunch.
45. One-track mind
Meaning:
Unable to think about anything else; narrow-minded.
In a Sentence:
Example 1: He has a one-track mind and can’t focus on anything but video games.
Example 2: Don’t expect him to consider other options; he’s got a one-track mind.
Other ways to say it:
Thick-headed, slow on the uptake, mind of a child.
46. Picking daisies
Meaning:
Daydreaming or mentally absent.
In a Sentence:
Example 1: He was picking daisies during the lecture and missed the entire explanation.
Example 2: Stop picking daisies and pay attention!
Other ways to say it:
Out to lunch, lights are on but nobody’s home, forgot to pay his brain bill.
47. Playing with a short stick
Meaning:
Lacking intelligence or ability.
In a Sentence:
Example 1: He’s playing with a short stick if he thinks he can finish this alone.
Example 2: Don’t expect much from her; she’s playing with a short stick.
Other ways to say it:
Not the sharpest tool in the shed, thick-headed, bonehead.
48. Sharp as a beach ball
Meaning:
Not very intelligent.
In a Sentence:
Example 1: He’s sharp as a beach ball and can’t understand simple instructions.
Example 2: That comment showed he’s sharp as a beach ball.
Other ways to say it:
Not the sharpest tool in the shed, not the brightest bulb in the box, as sharp as a marble.
49. So dense that light bends around him
Meaning:
Extremely slow to understand.
In a Sentence:
Example 1: He’s so dense that light bends around him; no matter how you explain, he doesn’t get it.
Example 2: Don’t waste your time—he’s so dense that light bends around him.
Other ways to say it:
Thick-headed, thick as two short planks, not the sharpest tool in the shed.
50. Someone who has a room temperature IQ
Meaning:
Very unintelligent.
In a Sentence:
Example 1: He’s got a room temperature IQ and can’t solve basic problems.
Example 2: That decision proves he has a room temperature IQ.
Other ways to say it:
Dumber than a box of rocks, bonehead, thick-headed.
51. Thicker than a whale omelette
Meaning:
Extremely stupid.
In a Sentence:
Example 1: He’s thicker than a whale omelette and can’t follow simple directions.
Example 2: Don’t expect him to understand—he’s thicker than a whale omelette.
Other ways to say it:
Thick as a brick, thick-headed, not the sharpest tool in the shed.
52. Thinks thunder is caused by angels bowling
Meaning:
Completely naive or ignorant.
In a Sentence:
Example 1: She thinks thunder is caused by angels bowling; that’s how clueless she is.
Example 2: If he believes that, he really thinks thunder is caused by angels bowling.
Other ways to say it:
Mind of a child, out to lunch, bats in the belfry.
Exercise 1 – Fill in the Blanks
Fill in the blanks with the correct idiom from the list of 52 idioms for stupid.
- When it comes to solving puzzles, Jake is definitely __; he takes forever to figure anything out.
- I don’t think you should trust his advice—he’s __ and often misses obvious details.
- She was completely __ during the meeting and didn’t respond to any questions.
- That idea is __; it won’t work no matter how you look at it.
- He’s a bit __; sometimes he says things that don’t make any sense at all.
- Don’t expect much from Tom in math class; he’s __.
- After the accident, people said he was __ and not himself anymore.
- You forgot your wallet again? You’re really __ today!
- The new guy is all muscle but no brain—he’s __.
- She’s __ and can’t understand even the simplest instructions.
- I think he’s __; he’s always daydreaming and seems mentally absent.
- That plan is crazy—he’s __ if he thinks it will succeed.
- He’s __; he just doesn’t get jokes or sarcasm.
- The wheel is spinning, but the hamster is dead perfectly describes someone who is __.
- Don’t be a __; think before you act.
- She’s __; she’s missing some important mental faculties.
Answer Key
- Slow on the uptake
- Not the sharpest tool in the shed
- Lights are on, but nobody’s home
- As much use as a chocolate teapot
- Got a screw loose
- Not the sharpest crayon in the box
- Missing a few marbles
- Not the brightest bulb in the box
- All brawn and no brains
- Thick as two short planks
- Out to lunch
- A few sandwiches short of a picnic
- Thick-headed
- Not playing with a full deck
- Bonehead
- A few cards short of a full deck
Exercise 2 – Multiple Choice Quiz
Choose the best answer for each question.
- What does the idiom “Not the brightest bulb in the box” mean?
A) Very intelligent
B) Not very smart
C) Very creative
D) Extremely confident - When would you say someone “Has a screw loose”?
A) They are very organized
B) They are mentally unstable or act strangely
C) They are very funny
D) They are very hardworking - Which idiom best describes someone who is mentally absent or not paying attention?
A) Out to lunch
B) Meathead
C) A few bricks short of a load
D) Bonehead - If someone is “A few sandwiches short of a picnic,” what does it imply?
A) They are hungry
B) They are not very intelligent
C) They are very friendly
D) They are very tired - What does “As much use as a chocolate teapot” mean?
A) Very useful
B) Completely useless
C) Very sweet
D) Very hot - Which idiom means “not thinking clearly or slow to understand”?
A) Thick as two short planks
B) Mad as a hatter
C) Got a screw loose
D) A one-track mind - If someone “Fell out of the stupid tree and hit every branch on the way down,” what are they?
A) Very clever
B) Extremely stupid
C) Very lucky
D) Very brave
Correct Answers
- B) Not very smart
- B) They are mentally unstable or act strangely
- A) Out to lunch
- B) They are not very intelligent
- B) Completely useless
- A) Thick as two short planks
- B) Extremely stupid
7 Tips to Remember
- Use idioms in daily conversation: Try to include idioms like “not the brightest bulb in the box” or “a few sandwiches short of a picnic” when talking with friends or colleagues. This helps make them part of your natural speech.
- Create mental images: Visualize the meaning of idioms. For example, imagine a light bulb that’s dim for “not the brightest bulb in the box” to remember it means someone not very smart.
- Group similar idioms together: Learn idioms with similar meanings like “not playing with a full deck”, “missing a few marbles”, and “a few cards short of a full deck” at the same time. This helps reinforce their meanings.
- Write sentences using idioms: Practice writing your own examples. For instance, write a sentence with “lights are on, but nobody’s home” to better understand how to use it.
- Listen and read actively: Pay attention when native speakers use idioms in movies, podcasts, or books. Hearing idioms in context makes them easier to remember.
- Use flashcards or apps: Make flashcards with the idiom on one side and the meaning plus an example sentence on the other. Review them regularly to strengthen your memory.
- Don’t be afraid to make mistakes: Using idioms might feel tricky at first, but practicing them in conversation—even if you make errors—will help you learn faster.
Conclusion
In this guide, you’ve explored many colorful English idioms that describe someone who might not be the sharpest or quickest thinker. You’ve learned their meanings, seen examples, and practiced with exercises to help make these expressions part of your vocabulary. Remember, idioms like “not the sharpest tool in the shed” and “a few bricks short of a load” add fun and personality to your English.
Try to use 2 or 3 idioms from this list today in your conversations or writing. The more you practice, the more natural they will feel. Keep exploring and enjoy speaking English with confidence!
