In a wild, reckless, or insane manner; acting or behaving in an extremely uncontrolled or senseless way.
From 'crazy' (emotionally unstable or insane), plus '-ly' suffix; 'crazy' itself has uncertain origins but possibly related to 'craze' meaning cracked pottery or breaking apart mentally.
We use 'crazy' casually for anything intense ('that's crazy good'), but the word originally described serious mental illness, so linguists watch how 'crazily' evolved from medical language to trendy slang—it shows how we've destigmatized old insult words.
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