The word "besoiled" means to become soiled or dirtied with oil, grease or mud. The antonym for this word would be "clean," meaning that something has been washed or wiped free of dirt or grime. Other antonyms for "besoiled" could include "sanitized," "purified," "gleaming," or "pristine." These words all suggest a state of cleanliness or purity, in sharp contrast to the dirty and grimy state that "besoiled" implies. Antonyms for "besoiled" are useful for describing a wide variety of situations, from glossy car engines to spotless kitchen counters.