Mouth"piece` (?), n.
1.
The part of a musical or other instrument to which the mouth is applied in using it; as, the mouthpiece of a bugle, or of a tobacco pipe.
2.
An appendage to an inlet or outlet opening of a pipe or vessel, to direct or facilitate the inflow or outflow of a fluid.
3.
One who delivers the opinion of others or of another; a spokesman; as, the mouthpiece of his party.
<-- hence (slang) a person's lawyer -->
Egmont was imprudent enough to make himself the mouthpiece of their remonstrance.
Motley.
© Webster 1913.