Akademik

bad hat
noun
someone who deliberately stirs up trouble (Freq. 1)
Syn: ↑troublemaker, ↑trouble maker, ↑troubler, ↑mischief-maker
Hypernyms: ↑unwelcome person, ↑persona non grata
Hyponyms:
agitator, ↑fomenter, ↑disturber, ↑heckler, ↑badgerer, ↑hellion, ↑heller, ↑devil, ↑hellhound, ↑instigator, ↑provoker, ↑inciter, ↑instigant, ↑firebrand, ↑loudmouth, ↑blusterer, ↑prankster, ↑cut-up, ↑trickster, ↑tricker, ↑hoaxer, ↑practical joker, ↑rioter

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noun
slang Britain : a disreputable dissolute person : bad egg

the man is a bad hat, a swindler or worse — Joyce Cary

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bad hat,
Especially British Slang. a corrupt or worthless person.

Useful english dictionary. 2012.