The word "un-smoothest" can be interpreted as something that is rough, bumpy, or uneven. Therefore, the antonyms for "un-smoothest" are words that describe something that is smooth, even, and polished. Some synonyms for smooth include effortless, gentle, and sleek. Words that describe a smooth finish include flawless, polished, and refined. On the other hand, antonyms for "un-smoothest" include words that describe something that is jagged, rough, or coarse. These words include coarse, bumpy, and uneven. Other words that describe something that is not smooth include rugged, unrefined, and jarring.