—n. 1. Anat.,Zool. a. the opening through which an animal or human takes in food.
b. the cavity containing the structures used in mastication.
c. the structures enclosing or being within this cavity, considered as a whole.
2. the masticating and tasting apparatus.
3. a person or animal dependent on someone for sustenance: another mouth to feed. 4. the oral opening or cavity considered as the source of vocal utterance.
5. utterance or expression: to give mouth to one's thoughts. 6. talk, esp. loud, empty, or boastful talk: That man is all mouth. 7. disrespectful talk or language; back talk; impudence.
8. a grimace made with the lips.
9. an opening leading out of or into any cavity or hollow place or thing: the mouth of a cave; a bottle's mouth. 10. the outfall at the lower end of a river or stream, where flowing water is discharged, as into a lake, sea, or ocean: the mouth of the Nile. 11. the opening between the jaws of a vise or the like.
12. the lateral hole of an organ pipe.
13. the lateral blowhole of a flute.
14. down in or at the mouth,Informal.dejected; depressed; disheartened: Ever since he lost his job, he has been looking very down in the mouth. 15. run off at the mouth,Informal.to talk incessantly or indiscreetly.
16. talk out of both sides of one's mouth, to make contradictory or untruthful statements.
—v.t. 1. to utter in a sonorous or pompous manner, or with excessive mouth movements: to mouth a speech. 2. to form (a word, sound, etc.) with the lips without actually making an utterance: She silently mouthed her answer so as not to wake her napping child. 3. to utter or pronounce softly and indistinctly; mumble: Stop mouthing your words and speak up. 4. to put or take into the mouth, as food.
5. to press, rub, or chew at with the mouth or lips: The dog mouthed the toys. 6. to accustom (a horse) to the use of the bit and bridle.
—v.i. 1. to speak sonorously and oratorically, or with excessive mouth movement.
2. to grimace with the lips.
3. mouth off,Slang. a. to talk back; sass: He mouthed off to his mother. b. to express one's opinions, objections, or the like in a forceful or uninhibited manner, esp. in public.