dis·be·lieve / ˌdisbəˈlēv/ • v. [tr.] be unable to believe (someone or something): he seemed to disbelieve her | [as adj.] (disbelieving) the disbelieving look in her eyes. ∎ [intr.] have no faith in God, spiritual beings, or a religious system: to disbelieve is as much an act of faith as belief.DERIVATIVES: dis·be·liev·er n.dis·be·liev·ing·ly adv.