blood bog

The act of using a female's period blood as lubrication while fucking them in the ass.

Bro 1: Yo brooo did you see that chick I had over last night?
Bro 2: Yeah bro did you bone her?
Bro 1: The red river was flowing, had to take the dirt road home through a blood bog.
Bro 2: Oh shit.. Nice determination - She had a killer ass.