Synonyms for Vast:

adj.

infinite (adjective)
endless, interminable, eternal, limitless, boundless.
large (adjective)
cavernous, sizable, magnificent, princely, ample, grand, elephantine, humongous, immense, big, grandiose, massive, comprehensive, majestic, awesome, gargantuan, expansive, extensive, great, capacious, impressive, giant, spacious, copious, soaring, enormous, mammoth, baggy, gigantic, bulky, towering, tremendous, roomy, lofty, prodigious, huge, generous, colossal, voluminous, large.
very large; wide in range (adjective)
capacious, detailed, monstrous, far-reaching, boundless, huge, big, ample, astronomical, mammoth, voluminous, gigantic, endless, spacious, far-flung, great, extensive, immense, limitless, comprehensive, massive, tremendous, giant, enormous, prolonged, widespread, eternal, prodigious, monumental, all-inclusive, titanic, colossal.

n.

high. mighty, jumbo, Gigantesque, monster, Massy, heroic, titanic, monumental, mastodonic, Brobdingnagian, Pythonic, mountainous, cyclopean, monstrous, behemoth, stupendous, whopping, herculean, walloping, Bunyanesque.

Other synonyms:

cyclopean, mastodonic, walloping, Bunyanesque, Massy, Gigantesque, Pythonic, boundless. monumental, titanic, mountainous, whopping. herculean, monstrous, heroic, stupendous. mighty. monster. high. Other relevant words:
detailed, behemoth, Massy, Bunyanesque, monstrous, stupendous, boundless, prolonged, high, cyclopean, Brobdingnagian, endless, heroic, Pythonic, herculean, monster, walloping, all-inclusive, jumbo, astronomical, mighty, monumental, Gigantesque, far-reaching, titanic, widespread, mastodonic, interminable, mountainous, far-flung, limitless, whopping, eternal.

Usage examples for vast

  1. In itself it was not so vast a step forward as might be thought. – Dawn of All by Robert Hugh Benson
  2. In all the vast world, he knew that the only friend Kiopo could rely on was himself. – Dusty Star by Olaf Baker
  3. I am talking particularly of the money question, the struggle for existence, which the vast majority of men are forced to make.... – The Sisters-In-Law by Gertrude Atherton