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: an erratic person : crackpot
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bug, crazy, fool, fruitcake, head case, loon, loony, lunatic, maniac, nut, nutcase, nutter [British slang], psycho, psychopath, sickie, sicko, wacko (also whacko)
circa 1570, in the meaning defined above
Resources for crackbrain
crack a smile
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noxious or harmful
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