academic costume UK /ˌæk.əˈdɛm.ɪk ˈkɒs.tjuːm/US /ˌæk.əˈdɛm.ɪk ˈkɑs.tjum/ noun1 •An outfit, typically consisting of a cap and gown, worn by academics on special occasions such as graduation. formsacademic costumes