To Beat Beat is used as an expression of ejaculating or Skeeting , To make the trouser snake sneeze on or spit on an object or objects , it can also be used as an alternative to saying something out of excitement such as Yes! or Alright!
Oh Shit I just passed my Biology Exam BEAT BEAT!!!, Get outta my face bitch before I Beat Beat in your eye, Dude look at her rack Beat Beat!
masturbating, jerking off
man, I need to go home and beat beat my meat