whack the bag
To jerk off profusively pounding on your sack.
I caught Gil whacking his bag today.
whack bag
the art of walking past one of your boys and giving him the little "love tap" back hand to his privates for sport.
Corey didn't expect the whack bag I layed on him in the line at Subway.
Whack Bag
A hard strike to ones genitals, Usually done with closed fist, or foot.
" All I did was poke her sisters tit and she freakin Whack Bagged me in the giggle berries!"