Smooth-tongued is an adjective used to describe someone who speaks in a convincing, persuasive manner. Antonyms for smooth-tongued could include terms like unconvincing, inarticulate, or halting. Other antonyms might include blunt, abrasive, or unrefined, as these terms indicate that a person is more forceful or direct in their communication. More indirect antonyms for smooth-tongued might include words like evasive, hesitant, or unclear, as these describe individuals who struggle to express themselves effectively. Overall, the antonyms for smooth-tongued encompass a range of qualities that might be considered less desirable in social, professional, or other contexts.