›very strange or foolish: She’s the craziest person I’ve ever met.[+ to infinitive]You’re crazy to rent the place without seeing it first.›Crazy can mean mentally ill.›Crazy can also mean behaving in a strange way esp. because of stress, as if you are mentally ill: The constant whine of the machine nearly drove (= made) me crazy.I think she’ll go (= become) crazy if she doesn’t take a vacation soon.crazily