Besoil, meaning to soil or dirty something, is a rare word that does not have many common antonyms. However, some words that can be considered antonyms for besoil include "clean," "purify," "sanitize," "whiten," "polish," "decontaminate," and "sterilize." These words indicate the removal or prevention of dirt, grime, or other contaminants. Besoil can also be seen as the opposite of "preserve," "protect," or "conserve," which refer to safeguarding or maintaining something in its original state. Overall, while besoil may not have direct antonyms, there are plenty of words that indicate the opposite action or result.