Delineate/Orate: In the sense that a person speaks clearly (as opposed to nonsensically) Focused/Composed: In the sense that a person has their ideas together. Quiet Down/Stay Silent: In the sense that a person is not speaking altogether.
The opposite (antonym) of antonym is synonym. An antonym is a word that means the opposite. A synonym is a word that means the same thing, or nearly the same thing, for a given context.
Some words do not have direct opposites [antonyms]. Antonyms do not usually substitute for phrases. The phrase "you are" has no antonym. A contrasting version of "you are" is "you are not".