In sexual kink community, a dominant non-monogamous sexual partner (often male) who gets significant sexual gratification from degrading a cuckhold. A partner in a Hotwife/cuckhold/Bull relationship
Wendy: "Our new bull is such a darkside bull, he made Bill sit on the floor and watch as he soaked my panties in my juices then the bull stuffed them in Billys mouth.
Sexual Kink Community term to describe a dominant (often male) sexual partner who enjoys deep sexual gratification from having sex with a married woman who isn't married to himself. Unlike a Darkside bull the humiliation of the cuckhold is not the primary motivation for this style of sexual kink activity though it isn't forbidden as part of the sexual session.
That lightside bull melted her brain into a puddle as her husband watched gleefully