The act of fisting both the anus and vagina of your sexual partner and then swinging them around like a battle axe in order to hit or attack objects/people.
Did you hear about Shaun, he tried double-fisted battle axing his girlfriend and hit a crowd of preschoolers.
Pauly Shore is the lingustic genuis who brought us "axing the weasel." It is a reference to masturbation, a violent form of masturbation. Like Pauly Shore's short-lived film career the phrase doesn't exactly make sense.
When I'm horny and angry at my penis, I pop in "Encino Man" and start axing the weasel.