1.) To mudturtle (or mudturtling) is a sex
act in which
someone goes down on a woman at the tail end of her period, when it's all brown. Derivation: the reptile, Mud Turtle, which lives alongside swamps and lakes.
2.) It can also refer to the final phase of a woman's period, in which the endometrium is drying up and brown.
1.) Man: Hey
baby, mind if I go downtown?
Woman: If you
don't mind mudturtling, I'm down.
The act is referenced in the comedy song "Mudturtle" by Purdy Hölsom.
2.) "My period is almost over; I'm mudturtling."