Vestigial refers to something that is no longer functional or necessary, and when we use the word "more vestigial", it implies that something has become even more useless or obsolete. The antonyms for this phrase are "less vestigial" or "fully functional". Less vestigial implies that something has retained a certain level of usefulness or relevance, while "fully functional" means that it is completely operational and serving its intended purpose. In biological terms, an organ may be fully functional, but it could also be vestigial if it no longer has a crucial role in the organism's survival. Therefore, the opposite of "more vestigial" would be either "less vestigial" or "fully functional" depending on the context.