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1.
Being angry or in a bad mood for seemingly no reason. Seen in Quadrophenia.
Chalky: Jimmy! Where you been?
Jimmy: Leave it out, will ya? I kipped on the beach!
Chalky: why you so umpy?

Bob: (Jokingly) Hey, faggot!
Ted: Fuck you , asshole, don't ever fucking call me a faggot or i'll beat your ass.
Bob: why're you so umpy?
by Mr nasty January 04, 2014