beat the cat
Female masturbation.
After a hard day at work, Amy decided to go home and beat the cat.
Beating Cat's Heart
Ask an unsuspecting victim if they have seen a 'beating cat's heart', followed by exposing one's testicles and pumping in and out of one's fist to mimic a beating heart.
Jeffrey: Hey William! Have you ever seen a Beating Cat's Heart?
William: I don't believe I have Jeffrey, please enlighten me!
William: I don't believe I have Jeffrey, please enlighten me!