halon UK /ˈheɪ̯.lɒn/US /ˈheɪ̯.lɔn/ noun1 •A hydrocarbon (more precisely, a haloalkane) in which one or more hydrogen atoms have been replaced by halogens.The Renew is also free of polyvinyl chloride, asbestos, chlorofluorocarbons and halons. — 2009 formshalons