masturbation done for the purpose of getting over lust for someone. The "it" in "rub it off" is the sexual attraction.
The term is similar to brush it off
, but is explicitly sexual.
If a hater
talks shit to you, you can brush it off and get on with your life. If a bad bitch
is stuck in your head, you can't brush it off: You gotta rub it off.
Holy shit! That girl on the airplane was so hot! I can't think knowing a chick that fine exists!
Dude, you're never going to see her again. Rub it off and get on with your life.