ostentatious adj. + Add to list US //ˌɑstənˈteɪʃəs// UK //ˌɒstəntˈeɪʃəs// os·ten·ta·tious SynonymsAntonymsEtymology Synonyms pretentious Antonyms unostentatiousOrigin Originated 1590; from Latin ostentātus + -ious.