Cuckolding is when the male partner is submissive and enjoys an element of humiliation as his wife or girlfriend has sex with other men. The male partner is called a cuck and the men the woman has sex with are called bulls.
The cuck will not be allowed to have sex with anyone else but usually will be made to watch. Sometimes he will orally service both his wife and the bull. Some cuckold couples enjoy the cuck being verbally abused.