an urban legend that holds that if you have vaginal or anal sex with a woman (or anal sex with a man) and punch him/her in the back of the head, it will somehow cause the vaginal/anal muscles to contract. this is medically impossible, but widely circulated among 12 year old boys and those that share their general level of maturity and/or a chauvanist animosity towards women. the only garanteed result of a donkey punch is an immediate end to your sex life and/or getting your ass kicked physically or in court.
"when you break up with your girlfriend, you should give her a donkey punch!"
1. the most important
2. a favorite girlfriend or boyfriend
3. a best friend, usually a dude, as in "my main man".
4. ebonics for "man"
5. main vein, the vein used to inject heroin, see also main lining
1. "if you're going to snort it, you might as well pop it, and if you're going to shoot it, you might as well main it" (from basketball diaries by jim carroll)
2. "that's my main girl"