Someone who is so grotesquely disgusting they aren’t even worth the energy to rape.
Allan – Hey man, did you see that lady?
Brent – That bitch is Unrapeable.
Unrapeable: define #2
Someone who is so gross, so disgusting, that he/she is not even worth raping. Someone who is repulsive, and whose genitalia is questionable even though they are a virgin.
Rory: Man, have you seen that Anna chick?
Steve: Yeah, dude; she’s unrapeable.