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bust (one's) ass
1. rude slang (acting upon oneself) To exert a significant amount of energy or work very hard to do, accomplish, or complete something. I've been busting my ass all night long to get this presentation ready for tomorrow's meeting. She's going to have to bust her ass if she wants a place on the varsity team.
2. rude slang (acting upon someone else) To harass, nag, or upbraid someone to do, accomplish, or complete something. The boss is busting everyone's ass to get the project ready by next week. Quit busting my ass! I'll get it done eventually!
vulgar slang To be flatulent; to fart. Who just busted ass? It stinks in here.