ASSIDUOUS Meaning of ASSIDUOUS in English [ ə'sɪdjʊəs ]■ adjective showing great care and perseverance.Derivatives~ly adverb~ness noun OriginC16: from L. assiduus , from assidere (see assess ), + -ous . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004