ad·ver·sar·i·al / ˌadvərˈse(ə)rēəl/ • adj. involving or characterized by conflict or opposition: industry and government had an adversarial relationship. ∎ opposed; hostile. ∎ Law (of a trial or legal procedure) in which the parties in a dispute have the responsibility for finding and presenting evidence: an adversarial system of justice. Compare with inquisitorial.DERIVATIVES: ad·ver·sar·i·al·ly adv.