Ringknocker 

Your balls and sack. When your girl is in the missionary position and you're fuckin' her in the twat, your balls bounce (knock) against her anus (ring).

Man, he's pounding her so hard, his balls have become a real Ringknocker.

Ringknocker by QueerBaitME October 29, 2009

Ringknocker 

The word ringknocker is a noun used to describe people who enjoy sutffing their cocks or other objects into people's anal or vaginal passages until they bleed profusely.

"Durling's mum is such a ringknocker. My ass is still bleeding and it's now got flaps!"
"Wow, i gotta get me some of that hot shit"

Ringknocker by jamthemaninspacewithamonkey March 14, 2005