Human testicles that possess the anthrometric property such that they repeatedly strike a sex partner's posterior (donk), typically but not necessarily during doggy style sex.
This is when you are having doggy style sex and just as you're about to blow your load you punch your mounted women in the back of the head causing vaginal constriction and maximum orgasmic pleasure. But be ware that you may knock her unconscious if you strike her too hard.
I was hosing my girlfriendlast night when I gave her a donky punch in the back of the head. I K.O.ed her but man was it worth it!