1. the part of a musical instrument, telephone, or other device that is placed in or near the mouth
2. a person who speaks on behalf of another person or organization
3. a protective device worn over the teeth during sports

Examples

• The trumpet player cleaned his mouthpiece after practice.
• She adjusted the mouthpiece on her telephone headset.
• The senator served as the party’s mouthpiece on healthcare issues.
• The company’s mouthpiece denied all allegations of wrongdoing.
• The boxer wore a mouthpiece to protect his teeth during the fight.
• The clarinet’s mouthpiece needs to be replaced.
• He became the unofficial mouthpiece for the student protesters.