mouthpiece

noun

1. a part that goes over or into the mouth of a person"the mouthpiece of a respirator"
2. an acoustic device; the part of a telephone into which a person speaks
3. a spokesperson (as a lawyer)
4. (especially boxing) equipment that protects an athlete's mouth
5. the tube of a pipe or cigarette holder that a smoker holds in the mouth
6. the aperture of a wind instrument into which the player blows directly