During anal sex, the person that is doing the penetrating and thrusting is the one that is doing the "knocking," and the anal opening is, obviously, referred to as the "back door."
by Zeeky H. Bomb March 19, 2005
Get the knocking on the back doormug. A condition in female humans wherein their breasts are too far around to the front of their chests. Clinically referred to as Crowded Cleavage Condition.
Opposite of bow chested.
Opposite of bow chested.
Dave: "Man, is Cindi knock chested or what?"
Kevin: "Way. I feel like her tits are always staring at me."
Kevin: "Way. I feel like her tits are always staring at me."
by Connie Lingquist November 4, 2010
Get the knock chestedmug. to fuck a girl in the ass, and right as you're about to cum, you punch her in the back of the head so she tenses up.
by Deez Nutz May 30, 2004
Get the knocking out the donkeymug. 
IE: you get your girlfriend pregnant and you did not use protection.
School of hard knocks says: Use protection because now you have another mouth to feed.
School of hard knocks says: Use protection because now you have another mouth to feed.
by lilshawn June 14, 2004
Get the school of hard knocksmug. "I went on a date last night but the sheila didn't put out so I had to go game and knock the top off it"
by Digger111 June 13, 2016
Get the Knock the top off itmug. by Lakelander March 5, 2018
Get the knock you offmug.