The Collaborative International Dictionary of English v.0.48:
gumshield \gumshield\ n. (Sport) A piece of athletic equipment that protects an athlete's mouth. Syn: mouthpiece. [WordNet 1.5]WordNet (r) 3.0 (2006):
gumshield n 1: (especially boxing) equipment that protects an athlete's mouth [syn: mouthpiece, gumshield]