When 2 or more individuals have excessive amounts of sex in a shower, bath tub, dank cave, or other distinctly moist area. One or both of the individuals will become extremely "pruney" and wrinkled. If the sex continues, either one, or both of the individuals is said to have a raisin fetish.
Dude: We've been in the shower a while, huh?
Chick: Yeah, I'm all pruney!
Dude: Like a raisin! I'm boning a raisin! This is so wrong... but so hot... I have a raisin fetish!
Chick: "OOOhhHHhhOoooHHoooOOohhh, I'm A RAAAAAIISSIIIN"