The meaning of CRAZY is not mentally sound : marked by thought or action that lacks reason : insane —not used technically. How to use crazy in a sentence.

CRAZY definition: mentally deranged; demented; insane. See examples of crazy used in a sentence.

Crazy can also mean behaving in a strange way esp. because of stress, as if you are mentally ill:

Use the adjective crazy to describe actions that aren't sensible, like the crazy way your brothers run around the house when their favorite team wins a game. Crazy can also mean "insane," though in …

If you describe someone or something as crazy, you think they are very foolish or strange.

CRAZY meaning: 1 : not sane: such as; 2 : having or showing severe mental illness

crazy (informal) used to describe someone whose mind does not work normally or whose behavior is very strange or out of control: Have you met the crazy old lady upstairs?

One who is or appears to be mentally deranged: "To them she is not a brusque crazy, but 'appropriately passionate'" (Mary McGrory).

to an extreme: We shopped like crazy and bought all our Christmas gifts in one afternoon. Idioms with great speed or recklessness: He drives like crazy once he's out on the highway.

There are 17 meanings listed in OED's entry for the adjective crazy, two of which are labelled obsolete, and one of which is considered offensive. See ‘Meaning & use’ for definitions, usage, and quotation …