Pronunciation: (mouth'pēs"),[key] —n. 1. a piece placed at or forming the mouth, as of a receptacle or tube.
2. a piece or part, as of an instrument, to which the mouth is applied or which is held in the mouth: the mouthpiece of a trumpet. 3. the part of a bit or bridle, as for a horse, that passes through the animal's mouth.
4. a person, newspaper, etc., that conveys the opinions or sentiments of others; spokesperson.
5. Slang.a lawyer, esp. a criminal lawyer.