opera slipper UK /ˌɒp.ə̯(ɹ).ə ˈslɪp.ə̯(ɹ)/US /ˌɔp.ə̯ɹ.ə ˈslɪp.ə̯ɹ/ noun2 •One's house slipper, cut low on both sides at the shank. •Synonym of opera pump. formsopera slippers