General:
* Mouth: The most basic and neutral term.
* Oral cavity: A more scientific term.
* Maw: A large or gaping mouth, often used in a figurative sense.
* Gills: (for fish)
* Beak: (for birds)
* Snout: (for animals with long noses)
* Jaws: The bones that form the mouth.
* Lips: The soft, fleshy parts that surround the mouth.
* Teeth: The hard structures used for chewing.
* Tongue: The muscular organ in the mouth used for taste, speech, and swallowing.
Appearance:
* Smiling: Expressing happiness or amusement.
* Pouting: Expressing sadness, displeasure, or sulkiness.
* Grim: Stern, serious, and unsmiling.
* Gaping: Wide open, often in surprise or shock.
* Pursed: Tightly closed, often in disapproval or thoughtfulness.
* Full: Plump and well-defined.
* Thin: Narrow and less defined.
* Dry: Lacking moisture, often due to dehydration.
* Chapped: Cracked and sore.
* Fleshy: Full and soft.
Action:
* Speaking: Using the mouth to produce sounds.
* Eating: Taking in food.
* Kissing: Pressing the lips together with another person.
* Yelling: Speaking loudly and forcefully.
* Whispering: Speaking softly and quietly.
* Chewing: Crushing food with teeth.
* Swallowing: Moving food from the mouth to the stomach.
* Breathing: Taking in air through the mouth.
Metaphorical:
* Mouthpiece: A person or organization that speaks for another.
* Word of mouth: Information spread by people talking to each other.
* Open your mouth: To speak freely or express an opinion.
* Shut your mouth: To be quiet or stop talking.
* Feed your mouth: To satisfy one's basic needs.
* Mouthwatering: Appealing to the sense of taste.
This is just a starting point. There are many other words you could use to describe a mouth, depending on the specific context.