When you deep throat so deep that you stick a ball in each cheek.

During a blowjob, a female may be able to deepthroat a man's cock. Truly experienced ladies can also engulf the balls into their mouth, causing them to have the appearance of a chipmunk storing nuts in the cheeks.

When one goes to a party where drinks are available, and procedes to stash the beers or bottles in their bag or coat, resembling a chipmunk stashing nuts in their mouth.

When its been a long time since a male has ejaculated, he fills his partners mouth up with so much cum... she looks like a Chipmunk

A trippy-monk.

To stab a girl's crotch violently with your penis.
It must go all the way into the crotch for it to be a "chipmunk"

A sexual act that occurs when a guy puts both of his testicles in his partners mouth, one in each cheek, and puts his penis down the back of his partner's throat.