got a screw loose

(idiom) crazy, not thinking properly

Example Sentence:

Mom: If you think I’m going skydiving, you’ve got a screw loose.
Son: Come on, mom!
Mom: No way!

If Steven thinks he can go out on a date with the most beautiful woman in school, he’s got a screw loose.

Similar idioms:

1. not all there
2. off one’s rocker
3. on second thought
4. you can’t teach an old dog new tricks
5. screw off
6. drive someone crazy
7. guts
8. a leopard can’t change its spots
9. balls
10. beauty is only skin deep
11. screw around
12. ace a test
13. screw around-2
14. screw up
15. full of oneself