Named after the American Thrash Metal band of the same name, the term Slayer may be used by a woman when telling others that she is menstruating. The term is a reference to Slayer's classic song "Raining Blood".
He asks her "Can I go down on you?"
She responds "It's not a good idea. I've got my Slayer"
"What do you mean?" he asks.
"I'm Raining Blood" she replies.