"Most tumaceous" is a term that describes something that is swollen or bloated. The antonyms for this term would be words that indicate something that is thin, flat, or compact. Some of the antonyms for "most tumaceous" could include words like "slim," "skinny," "svelte," "lean," "narrow," "thin," or "compressed." These words describe something that is the opposite of swollen or bloated and could be used to convey different meanings or feelings in a sentence. For example, instead of saying "the most tumaceous pillow," one could say "the flattest pillow" to indicate a different quality.