Synonyms for Mouthpiece (same or very similar meaning)
WordNet sense 1 (a spokesperson (as a lawyer)):
mouth, mouthWordNet sense 2 ((especially boxing) equipment that protects an athlete's mouth):
gumshieldWordNet sense 3 (the aperture of a wind instrument into which the player blows directly):
embouchureFrom the ODE community, based on WordNetadd/edit