DIADEM Meaning of DIADEM in English [ 'dʌɪədɛm ]■ noun a jewelled crown or headband worn as a symbol of sovereignty.Derivatives~ed adjective OriginME: from OFr. ~e , via L. from Gk diadēma , from diadein 'bind round'. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004