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
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