Gast \Gast\, v. t. [OE. gasten, g?sten to frighten, akin to Goth. usgaisjan. See Aghast, Ghastly, and cf. Gaze.]

To make aghast; to frighten; to terrify. See Aghast. [Obs.]

--Chaucer. Shak.

Source: Webster's Revised Unabridged Dictionary (1913)