The muscle inside the
vagina (cunt).
This was used as an insult in the
HBO hit series Entourage where
character Ari Gold (played by Jeremy Piven) told character "E" that he was a cunt muscle for waking his family up in the early morning.
E: looks like i woke u up this
time huh Ari?
Ari: Noo but u did wake my wife and kids dick
head, Vinnie better be sitting in
prison with a DUI or something is he?
E: No.
Ari: Then what the fuck do u want Cunt Muscle!?