"fouling" in the verb sense
hit a foul ball
2. pollute, foul, contaminate
"The industrial wastes polluted the lake"
3. clog, choke off, clog up, back up, congest, choke, foul
become or cause to become obstructed
"The leaves clog our drains in the Fall"
"The water pipe is backed up"
commit a foul break the rules
5. foul, befoul, defile, maculate
spot, stain, or pollute
"The townspeople defiled the river by emptying raw sewage into it"
"foul the water"
become soiled and dirty
Source: WordNet® (An amazing lexical database of English)
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