Refers to a person in a relationship who doesn't "put out." Typically it is a woman who does not want to have sex even in a committed relationship, but it can also refer to a guy not pleasing his woman or not committed to the relationship.
Dude: Man, my girl totally refuses to have sex with me.
Dude's Friend: Well we know who wears the chastity belt in the relationship!
Dude's Friend: Well we know who wears the chastity belt in the relationship!
by XonyMudd July 24, 2010