The Donkey Punch is when your engaged in anal sex and when your about to ejaculate you punch the poor little lady in the back of the head so her anal cavity tightens making the orgasm all that more better (for you ofcourse).
In most countries it would be illegal to donkey punch a donkey. Because being sexually involved with an animal is considered bestiality and donkey punching a donkey is animal cruelty. But to answer...