Some one who doesn't know how to pull up their saggy pants (mainly chicks)
That sacker Crack needs to pull up her pants!
A man who tucks they’re nuts and you can see them from the back.
Your a Back Sacker because I can see your nuts from the back
Someone who hits someone else in the ballsack.
Person 1: "Dude, Trey just hit me in the balls!"
Person 2: "Wow, I didn't know that he was a Sacker."