To slap one's testicles across another individual's face (esp. forehead). Similar to tea bagging, however in this case the sack is not rested on the deponent, but rather used as an instrument of assault.
Speed bagging is often done to humiliate and/or shame the person upon which it is inflicted. It is also valuable for its humorous quality.
This activity is solely engaged in between males, and would be frowned upon as vulgar and inappropriate if executed upon a female. As with tea-bagging, this act is never considered homoerotic, although the deponent might be derided as a "fag" anyway.
The next time you black out I'm gonna fuckin speed bag your faggot ass, you fuckin light-weight.