| verb | hit a foul ball |
| verb | make impure “The industrial wastes polluted the lake” |
| verb | become or cause to become obstructed “The leaves clog our drains in the Fall” |
| verb | commit a foul; break the rules |
| verb | spot, stain, or pollute “The townspeople defiled the river by emptying raw sewage into it” |
| verb | make unclean “foul the water” |
| verb | become soiled and dirty |
| adjective | made dirty or foul “a building befouled with soot” |
| adjective | especially of a ship's lines etc “with its sails afoul” |
| foul | noun | an act that violates the rules of a sport |
| pollution | noun | the state of being polluted |
| polluter | noun | a person or organization that causes pollution of the environment |
| pollutant | noun | waste matter that contaminates the water or air or soil |
| contaminative | adjective | making impure by contact or mixing |
| contamination | noun | a substance that contaminates |
| contaminant | noun | a substance that contaminates |
| clog | noun | any object that acts as a hindrance or obstruction |
| backup | noun | an accumulation caused by clogging or a stoppage |
| congestive | adjective | relating to or affected by an abnormal collection of blood or other fluid |
| congestion | noun | excessive crowding |
| befoulment | noun | the state of being polluted |
| defilement | noun | the state of being polluted |
| defiler | noun | a person or organization that causes pollution of the environment |
| macula | noun | a patch of skin that is discolored but not usually elevated; caused by various diseases |
| maculation | noun | the act of spotting or staining something |