a type of chemical compound in which three of the hydrogen atoms in a methane molecule have been replaced by halogen atoms, esp by chlorine in drinking water. Trihalomethanes are thought to be carcinogenic
trihalomethane in American English
(traɪˌhæləˈmɛθˌeɪn)
noun
any of a family of organic chemical compounds, including chloroform, that form as when water supplies are chlorinated