A wolfback is a sexual act in which a male is penetrating a female's ass. While doing this, the male reaches around and sticks his finger/fingers down the female's throat, inducing her to vomit. Through the contracting of her sphincter muscles, her ass tightens, increasing the male's pleasure and sensation.
Anal sex, finger(s) down throat, pukes, ass tightens = greater sensation
by Arch Knacker May 09, 2005