look up any word, like spook:
After attempting to start some sexy times with your wife or girlfriend by rubbing your hard-on on her leg or against her back you get rejected or ignored, the respectable thing to do is hide your boner in the mattress by laying on your stomach.

Also referred to as Mattress Peen
I tried to sex up my lady last night but ended up with mattress Penis
by Can of Peas February 07, 2010