Receipient of bad luck, primarily when least expected, and usually of great weight. A Dack is usually called "gay" even if not a homosexual.
by Russ March 12, 2004
Get the dackmug. 
Done in doggy style position. After ejaculation, use your last thrust to break your partner's neck against the bed post.
by russ March 29, 2004
Get the bulldozermug. 