any of a group of chlorinated isomers of biphenyl, formerly used in the form of a toxic, colorless, odorless, viscous liquid, esp. as an insulator in electrical equipment
See PCB in American Heritage Dictionary 4
(pēˌsē-bēˈ)
noun
Any of a family of industrial compounds produced by chlorination of biphenyl, noted primarily as an environmental pollutant that accumulates in animal tissue with resultant pathogenic and teratogenic effects.