The term 'most foul' can be described by four different crossword solutions: vilest (6 letters), LOWEST (6 letters), rankest (7 letters), and smelliest (9 letters). Vilest is an adjective meaning extremely wicked or vile, while LOWEST is an adjective meaning of the least or smallest degree or amount. Rankest is an adjective meaning having a strong, unpleasant smell, and smelliest is an adjective meaning having the strongest, most unpleasant smell. All four words are used to describe something that is considered to be the most foul.