waste matter that contaminates the water or air or soil
"The factory was fined for dumping toxic pollutant into the nearby river, which killed thousands of fish."
A foreign substance that makes something dirty, or impure, especially waste from human activities.
"The factory's smokestacks released a thick cloud of pollutant into the air, making the nearby neighborhood feel like it was covered in invisible grime."
The word pollutant comes from the Latin verb polluere, meaning to make unclean or defile, combined with the suffix -ant to indicate something that performs the action. It essentially refers to a substance that causes pollution.