In baseball terminology, a brushback is a pitch, often used for intimidation purposes, thrown near a batter's head. A pitcher will throw a brushback if he thinks the batter is crowding over the plate, is being a showboat, or for retaliation.

Brushbacks can result in warnings, ejections, or even bench-clearing brawls.
Nolan Ryan threw a brushback at Robin Ventura years ago...and then proceeded to administer a grade-A asswhoopin' on the poor guy.
by howlincoyote2k1 February 26, 2007
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The act of accidentally brushing your penis against the toilet seat / bowl when sitting down.
A: Man, I went to take a shit and got brushback when I stood up.
B: Dude, weak.
by toomanyswans January 3, 2015
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