1. 
[syn: huge, immense, vast, Brobdingnagian]
The Collaborative International Dictionary of English v.0.48:
Vast \Vast\, n.
   A waste region; boundless space; immensity. "The watery
   vast." --Pope.
   [1913 Webster]
         Michael bid sound
         The archangel trumpet. Through the vast of heaven
         It sounded.                              --Milton.
   [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Vast \Vast\ (v[.a]st), a. [Compar. Vaster (v[.a]st"[~e]r);
   superl. Vastest.] [L. vastus empty, waste, enormous,
   immense: cf. F. vaste. See Waste, and cf. Devastate.]
   [1913 Webster]
   1. Waste; desert; desolate; lonely. [Obs.]
      [1913 Webster]
            The empty, vast, and wandering air.   --Shak.
      [1913 Webster]
   2. Of great extent; very spacious or large; also, huge in
      bulk; immense; enormous; as, the vast ocean; vast
      mountains; the vast empire of Russia.
      [1913 Webster]
            Through the vast and boundless deep.  --Milton.
      [1913 Webster]
   3. Very great in numbers, quantity, or amount; as, a vast
      army; a vast sum of money.
      [1913 Webster]
   4. Very great in force; mighty; as, vast labor.
      [1913 Webster]
   5. Very great in importance; as, a subject of vast concern.
      [1913 Webster]
   Syn: Enormous; huge; immense; mighty.
        [1913 Webster]
WordNet (r) 3.0 (2006):
vast
    adj 1: unusually great in size or amount or degree or especially
           extent or scope; "huge government spending"; "huge
           country estates"; "huge popular demand for higher
           education"; "a huge wave"; "the Los Angeles aqueduct
           winds like an immense snake along the base of the
           mountains"; "immense numbers of birds"; "at vast (or
           immense) expense"; "the vast reaches of outer space";
           "the vast accumulation of knowledge...which we call
           civilization"- W.R.Inge [syn: huge, immense, vast,
           Brobdingnagian]
Moby Thesaurus II by Grady Ward, 1.0:
80 Moby Thesaurus words for "vast":
   Atlantean, Brobdingnagian, Cyclopean, Gargantuan, Herculean,
   Homeric, abysmal, ample, amplitudinous, astronomic, astronomical,
   awesome, behemoth, big, boundless, broad, bulky, capacious,
   colossal, commodious, cosmic, deep, elephantine, endless, enormous,
   epic, expansive, extended, extending, extensive, far-flung,
   far-reaching, galactic, giant, giantlike, gigantic, great, heroic,
   huge, humongous, immeasurable, immense, incalculable,
   indeterminate, inexhaustible, infinite, interminable, jumbo,
   king-size, large, limitless, mammoth, massive, massy, measureless,
   mighty, monster, monstrous, monumental, mountainous, never-ending,
   outsize, overgrown, prodigious, profound, roomy, sizable, spacious,
   spreading, stupendous, titanic, towering, tremendous, unbounded,
   unlimited, voluminous, weighty, whopping, wide, widespread
V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):
VAST
       Virtual Archive Storage Technology