Sack Back 

When one man places his sack on another man's back. Used in the penis showing game

Wacko:(standing shirtless working out)I love working out
Ed: (standing naked)I love my sack on people's backs
(jumps on Wacko's back, and his sack is on Wacko's back, thus giving him sack back)
Wacko: God damn it Ed!
Ed: Gotchya Wacko!
(Proceeds to kick Wacko in the ass twice)

Sack Back by I Cruuuuuuuuuuuuuuuuuuunch you May 24, 2009

Sack Back 

When someone gives you a piggy back ride and your balls are on their back...raw.

I was drunk in the shower and fell. He gave me a piggy ride to the ER then I gave my friend sack back on the way there.

Sack Back by Sugar Flaps August 20, 2021

tuck your sack back 

Grabbing your package and putting it in upwards of your butt cheeks.

Do Not tuck your sack back, we are Powerhouse!

tuck your sack back by Bitty Bitt December 28, 2016

Sack to Back or Sac to Back 

Sack to back is the term used when two males ride a motorcycle or scooter together.
Also referred to as "Butts to Nuts"

Those guys are riding "Sack to Back or Sac to Back"

Sack to Back or Sac to Back by Indetrucks March 4, 2011

Sack the back 

To penetrate an anus. Anal sex. Sack to have sex and back as in the behind.

Man that girl looks kinky, i bet she'd let me sack the backQ

Sack the back by ToeKnee September 17, 2005

back sack attack 

The assault of one's testicles from behind. Generally, the victim is bent over, however a standing attack up the legs is also commonplace.

Often times, the assailant will yell "back sack attack!" either at contact, or after the strike is complete.

Winding up for a kick, Ben positioned himself behind a bent-over Matt. Using mostly the flick of his foot unto the scrotum, Ben yelled "Back sack attack!" before Matt ever got the chance to react. Devolving into his fetal position, Matt sat writhing in pain.

back sack attack by MrPistachio February 9, 2013

Back-sack 

Back Sack is the backside of ones scrotum.

A: Yo dog, I can't believe you just ball-tapped me from behind, you got all back-sack.
B: Ew, check out that old guy's back-sack hanging out of his pants.
C: Check out Katz's shaved back-sack.
D: Mom, Jacob put his back-sack on my face.

Back-sack by J'Nathan Bo'Jingles May 25, 2008