When a girl is giving head on her knees whilst the man stands, and she punches the scrotum repeatedly like a boxer punching a speed bag.
Hilary: So last night me and Ryan went out to dinner...
Friend: How was it?
Hilary: That asshole was staring at the waitress' ass the whole time, but i played it cool. So when we got home he thought he was just getting a BJ, but when i got on my knees I gave 'em a good old fashioned speedbagging.
(Speedbaged): when your sitting and fart and it rides up frontwards and hits your sac repeatedly. The longer you pass gas, the more your sac gets hit like a (speedbag).
"man I just let one go and (speedbaged) my sac. "
" a few things a womon can't do and one of them is give herself a (speedbag)"
"don't you hate when you (speedbag) yourself so hard, you almost drop to your knees
Preferably preformed in a warmer environment to allow the balls to droop to a sufficient level, a female (or male) based off preference. Will then preform a speed bag technique commonly preformed in boxing to said nuts.