1. vulgar 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 a nut to get this presentation ready for tomorrow's meeting.He's going to have to bust a nut if he wants a place on the varsity team.
2. vulgar slang To ejaculate.
bust a nut
1. tv. to ejaculate. I almost busted a nut when I saw her bend over.
2. tv. to work hard to accomplish something. I busted a nut to get it done on time.