Sack Smacking 

Sexual activity involving the intentional smacking, flicking, punching, kicking or striking of the male ballsack for gratification. May involve hitting with the hand or other device such as a riding crop.

I hired a DOM off the internet and she tied me up and did some sack smacking. Hurt like hell but we both enjoyed the experience.

Sack Smacking by Eaton Holgoode April 26, 2017

Smackin' the Sack 

1) The act of constantly abusing your genitals to pleasurable thoughts
2) Slang for playing the game of Hacky Sack

1) "Jeff's kinda weird, he says that instead of masturbating, he usually just smacks the sack."
2) Man 1: Hey what are you doing?

Man 2: Nothin' much just smackin' the sack, you want in?

Man 1: Sure!

Smackin' the Sack by TheCyclopsMan December 9, 2011

Sacksmacking 

Any action in which, during sexual intercourse, the male genitalia hits any part of the female's body. Most common while having sex doggy-style when the male's testicles are hanging loose and they slap the female's pubes during thrusting

Man, that pornstar's balls are hung and he's banging the chick doggystyle! Check out the sacksmacking dude!!

Sacksmacking by hanginghorse87 August 20, 2010