Ballgag

A gag—an object placed in or over a person's mouth so as to prevent speech—may be used in sexual bondage and BDSM roleplay. Gags are usually associated with roleplays involving bondage, but that is not necessarily the case. The person who wears the gag is regarded as the submissive partner, while the other is regarded as the dominant one. People may wear gags for a variety of reasons. Some people derive erotic pleasure from a gag, either in a submissive or dominant role. When combined with other physical restraints, the wearing of a gag can increase the wearer's sense of helplessness and anxiety level within a BDSM scene by rendering them unable to speak during sexual activity, which some people enjoy.