Sweat that compiles directly behind the balls during a jerk-off sesh/sexual intercourse. It is called dog butter because the female licks it off of your skin like a dog.
Ex. 1: Yo, that broad is totally craving my dog butter, bra.
Ex. 2: Yo, I prodced so much fin' dog butter when I gave myself a dutch rutter last night.
Ex. 3: Yo, I put all my dog butter in a jar for you.