A relationship which survives for the most part on sex, hence there is very little relation, mostly penetration.
Matt can't come to the movies tonight, he's too committed to his penetrationship.
1. A word used to describe a relationship where there is little or no "relation", mostly penetration.
2. See fuck buddies
"I'm sick of all this touchy feely crap, relationships are too demanding, I want a penetrationship!"