Source : Webster's Revised Unabridged Dictionary (1913)

Vast \Vast\, a. [Compar. {Vaster}; superl. {Vastest}.] [L.
   vastus empty, waste, enormous, immense: cf. F. vaste. See
   {Waste}, and cf. {Devastate}.]
   1. Waste; desert; desolate; lonely. [Obs.]

            The empty, vast, and wandering air.   --Shak.

   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.

            Through the vast and boundless deep.  --Milton.

   3. Very great in numbers, quantity, or amount; as, a vast
      army; a vast sum of money.

   4. Very great in importance; as, a subject of vast concern.

   Syn: Enormous; huge; immense; mighty.

Vast \Vast\, n.
   A waste region; boundless space; immensity. ``The watery
   vast.'' --Pope.

         Michael bid sound The archangel trumpet. Through the
         vast of heaven It sounded.               --Milton.

Source : WordNet®

vast
     adj : 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}, {Brobdingnagian}]