V. To stick one's face into the crack of a voluptuous booty (clothed or not). For optimal butt-snorkeling, the butt should be plump enough to surround the face in an air-tight seal, the way a normal snorkeling mask would. Essentially the booty equivalent of motor boating.
Person 1: "That is the finest ass I've ever seen."
Person 2: "What I wouldn't do to butt-snorkel that beauty!"
