Entry 1 sense Webster, 1913 Flabbergast /(flăb"bẽr*găst)/ · Flab·ber·gast · IPA /ˈflæbɚˌɡæst/ 01 v. t. To astonish; to strike with wonder, esp. by extraordinary statements. 1. To astonish; to strike with wonder, esp. by extraordinary statements.[Jocular]