ADVENTITIA Meaning of ADVENTITIA in English [ ˌadvɛn'tɪʃə ]■ noun the outermost layer of the wall of a blood vessel.Derivatives~l adjective OriginC19: shortening of mod. L. tunica ~ 'additional sheath'. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004