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English definition of “crazy”

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crazy

adjective  /ˈkreɪ·zi/ us  
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
adverb [not gradable]  /ˈkreɪ·zə·li/ us  
craziness
noun [U]  /ˈkreɪ·zi·nəs/ us  

crazy

noun [C usually pl]  /ˈkreɪ·zi/ infml us  
a person who acts in a strange or threatening way, esp. one who is mentally ill: Are we talking about a bunch of crazies or about a legitimate military force?
(Definition of crazy from the Cambridge Academic Content Dictionary © Cambridge University Press)
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