The word "most ungrounded" refers to something that is lacking in evidence or logical reasoning. The opposite of this would be something that is well-founded, established, or proven. Synonyms for "grounded" include practical, sensible, and rational. Antonyms for "ungrounded" might include grounded, stable, solid, strong, or grounded in reality. Examples of antonyms for "most ungrounded" might include "firmly established," "well-supported," or "backed by evidence." Antonyms can help to create a more nuanced understanding of language and expand one's vocabulary in new and diverse ways.