Foulest

adjective

1. Covered with, or containing unclean matter; dirty.

   "A ship's bottom is foul when overgrown with barnacles"

2. (of words or a way of speaking) obscene, vulgar or abusive.

   "His foul language causes many people to believe he is uneducated."

3. Detestable, unpleasant, loathsome.

   "He has a foul set of friends."

4. Disgusting, repulsive; causing disgust.

   "There was a foul smell coming from the toilet."

5. Ugly; homely; poor.