A spunk trough is that hollow at the bottom of a womans back, right on her spine, that appears when she's on her hands an knees. It is most prevelant when she arches her back during doggy style. The goal is to fill it.
She was bent over the bed and I was getting her from behind. I pulled out just in time to finish on her back and nearly filled her spunk trough.
by DQL21 February 12, 2016