impugnto dispute the truth, validity, or honesty of a statement or motive; to call into questionThe lawyer sought to impugn the credibility of the key witness during cross-examination.NoteThe lawyer sought to impugn the credibility of the key witness during cross-examination.Elon.io is an online learning platformWe have an entire course teaching GRE Verbal — Essential Vocabulary grammar and vocabulary.Start learning GRE Verbal — Essential Vocabulary now