corpsing
To fornicate with someone who is not taking an active role, usually out of nervousness or disinterest in their partner, but because of its macabre allusion to necrophilia, it is not unforeseeable that it could be because the person is non-consenting.
"Man, last night I was with Amy, and when we went up to her bed, she just laid there like a corpse; it wasn't no fucking, it was corpsing!