'Halogen' definitions:
Definition of 'halogen'
From: WordNet
noun
Any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions
Definition of 'Halogen'
From: GCIDE
- Halogen \Hal"o*gen\ (h[a^]l"[-o]*j[e^]n), n. [Gr. "a`ls, "alo`s, salt + -gen: cf. F. halog[`e]ne.] (Chem.) An electro-negative element or radical, which, by combination with a metal, forms a haloid salt; especially, chlorine, fluorine, bromine, and iodine; sometimes, also cyanogen. See Chlorine family, under Chlorine. [1913 Webster]