An unexpected interruption (usually by a figure of authority) during an intimate moment in the backseat of a vehicle, or other public place.
Ashlee and Duke had their privacy invaded with a knock of shock, as they were getting busy in the back of his car.
by A cat and a flamingo August 6, 2007

Used if a prior arrangement is terminated by either party usually due to laziness, a lack of interest or tiredness.
Turn it in
Turn it in
Joe - "You still wanna go to the club tonight?"
Pete - "Nah, knock it on the head mate, im too tired!"
Pete - "Nah, knock it on the head mate, im too tired!"
by Wibbsy October 3, 2003

When you knock on someone's door and run away so you mess with their heads and they think they imagined it.
by Flickoh February 23, 2006

by BigFishyBob March 29, 2007

by Grove street March 19, 2018

by Theshart September 19, 2014

When a topless or nearly topless woman's breasts are slapping together, caused by a back and forth motion during vigorous activities, such as sex or jogging
by Mouse3008 May 26, 2015
