Alligator Head
When an adult human male is receiving a Fellatio from an adult human female and the females eyes roll behind her head revealing vertical reptilian pupils as she snaps her jaw onto the base of the males penis. She then begins to twirl and twist, tearing the males genitalia, simulating the alligator death roll.
I couldn't be with Gina anymore, she tried giving me that alligator head so I had to get the the hell out of there!