1. large, enormous, huge. vastvast, n. a waste region; boundless space; immensity. the watery vast. michael bid sound the archangel trumpet. through the vast of heaven it sounded.vast vast , a. [compar. vaster ; superl. vastest.] [l. vastus empty, waste, enormous, immense: cf. f. vaste. see: waste, and cf. devastate.]