Entry 2 senses · 2 variants Webster, 1913 Agast · A·gast · IPA v. t. p. p. & a. 01 v. t. To affright; to terrify. 1. To affright; to terrify.[Obs.] 02 p. p. & a. See Aghast. 1. See Aghast. See: Aghast