When you're sucking someone's balls and their hairy scrotum triggers the gag reflex, and you cough up the balls.
I was feasting on a couple of nuts last night and coughed up a furball. Meow!!
by Chuck Norris's balls November 24, 2005
those tiny hairs that get stuch in the back of your throat after cunnilingus.
Ugh I got a furball stuck in my throat and it gaging me.
by Chickenman June 12, 2003