DELETERIOUS Meaning of DELETERIOUS in English [ ˌdɛlɪ'tɪərɪəs ]■ adjective formal causing harm or damage.Derivatives~ly adverb OriginC17: via med. L. from Gk dēlētērios 'noxious' + -ous . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004