1 part of a telephone
VERB + MOUTHPIECE cover (up), put your hand over He put his hand over the mouthpiece and called his wife to the phone.
2 sb/sth that informs the public about sb/sth's opinions
ADJ. official, political
VERB + MOUTHPIECE act as, be
PREP. ~ for/of The media is controlled by the state and acts as a mouthpiece for the ruling party.