What is "trihalomethane"

n. (context organic chemistry English) Any of many halogenated derivatives of methane containing three (not always the same) halogen atoms; many are environmental pollutants

Trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane (CH) are replaced by halogen atoms. Many trihalomethanes find uses in industry as solvents or refrigerants. THMs are also environmental pollutants, and many are considered carcinogenic. Trihalomethanes with all the same halogen atoms are called haloforms. Several of these are easy to prepare through the haloform reaction.