What it usually means
The mouth does two of the most basic things a person does: it speaks and it eats. Dreams about mouths usually concern one or both of these — what comes out of you in words, and what goes into you as nourishment, influence or pressure.
Speech is the most common theme. A dream mouth that cannot open, cannot make a sound, or says the wrong things often reflects something unsaid in waking life: a protest swallowed, a truth held back, a feeling that has not found words. These dreams tend to appear when a person feels silenced or does not yet dare to speak.
The opposite also happens. Dreams of saying too much, shouting or being unable to stop talking often come after a conversation in which you revealed more than you meant to, or when you fear that something private will slip out.
Taking in is the second theme. Eating, tasting, swallowing and spitting out are all ways of deciding what becomes part of you. A dream about the mouth can be about what you accept — ideas, demands, relationships — and what you refuse.
People who live in a second language sometimes dream of mouths that will not form the right words. Such dreams often reflect the daily effort of being understood, and they usually ease as the new language settles.
Worth saying plainly: the mouth is busy during sleep. Dry mouth, sleeping with the mouth open, clenching the jaw or grinding the teeth can all enter dreams directly. If you wake with a sore jaw, the body may be part of the dream's meaning.
What changes the meaning
Unable to speak. Feeling silenced; something important left unsaid.
A mouth sewn or taped shut. Being prevented from speaking, by others or by your own fear.
Talking without control. Fear of revealing too much; pressure to be open.
A large or open mouth. Hunger, need, or a wish to take in more.
A mouth full of something. Too much to process; words or feelings you cannot swallow.
Spitting something out. Rejecting an idea, influence or role.
A bleeding mouth. Hurt connected with something said — by you or to you.
Someone covering your mouth. Being kept quiet; a secret you are asked to keep.
Kissing. Closeness, intimacy, exchange — what passes between two people.
A mouth without lips or teeth. Feeling powerless in speech; unable to bite back.
Lipstick or painted lips. How you present your words; a mask on what you say.
A smiling mouth. Openness and warmth, or a smile that hides something.
When it keeps coming back
Recurring mouth dreams often accompany situations where speaking up is difficult — at work, in a family, in a relationship where your words have little weight.
They also return after conflicts in which something important was said or left unsaid, until the matter is resolved.
If you keep dreaming that you cannot speak, try writing down what you were trying to say in the dream. Often the sentence is waiting, complete, just behind the silence.
In Jungian terms
Jung's first scientific reputation came from the mouth. As a young doctor at the Burghölzli clinic in Zurich he used the word association experiment: a list of words was read aloud, and the patient answered each with the first word that came to mind. Jung noticed that hesitations, stumbles and odd replies clustered around particular themes, and from those disturbances he built his idea of the complex — a knot of emotion that makes words catch in the throat.
Jungian readers find the same knots in dreams about mouths. Where speech fails in a dream, a complex is often near, holding something with more feeling attached than the dreamer has yet admitted.
A blocked mouth, in that sense, is a signpost. It marks the exact spot where something important is waiting to be said.