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 24, 2015
Boob knocked. To be boob knocked means to be smacked in the face with some large breasts so much so that a nipple shaped impression can often be left on one's cheek.
by Bum face May 01, 2006