The term "most full-mouthed" implies someone or something that is extremely expressive and verbose. The antonyms for this phrase include understated, reticent, terse, succinct, and concise. These words describe someone who is reserved, speaks only when necessary, and chooses their words carefully. They are the opposite of someone who is "most full-mouthed," who tends to be loud and overpowering in their communication style. While being full-mouthed can be beneficial in certain situations like public speaking or sales, understated and concise language is often appreciated in business settings or personal relationships where clarity and precision are valued.