The Collaborative International Dictionary of English v.0.48:

Enormous \E*nor"mous\, a. [L. enormis enormous, out of rule; e
   out + norma rule: cf. F. ['e]norme. See Normal.]
   1. Exceeding the usual rule, norm, or measure; out of due
      proportion; inordinate; abnormal. "Enormous bliss."
      --Milton. "This enormous state." --Shak. "The hoop's
      enormous size." --Jenyns.
      [1913 Webster]

            Wallowing unwieldy, enormous in their gait.
                                                  --Milton.
      [1913 Webster]

   2. Exceedingly wicked; outrageous; atrocious; monstrous; as,
      an enormous crime.
      [1913 Webster]

            That detestable profession of a life so enormous.
                                                  --Bale.

   Syn: Huge; vast; immoderate; immense; excessive; prodigious;
        monstrous.

   Usage: -- Enormous, Immense, Excessive. We speak of a
          thing as enormous when it overpasses its ordinary law
          of existence or far exceeds its proper average or
          standard, and becomes -- so to speak -- abnormal in
          its magnitude, degree, etc.; as, a man of enormous
          strength; a deed of enormous wickedness. Immense
          expresses somewhat indefinitely an immeasurable
          quantity or extent. Excessive is applied to what is
          beyond a just measure or amount, and is always used in
          an evil; as, enormous size; an enormous crime; an
          immense expenditure; the expanse of ocean is immense.
          "Excessive levity and indulgence are ultimately
          excessive rigor." --V. Knox. "Complaisance becomes
          servitude when it is excessive." --La Rochefoucauld
          (Trans).
          [1913 Webster]

WordNet (r) 3.0 (2006):

enormous
    adj 1: extraordinarily large in size or extent or amount or
           power or degree; "an enormous boulder"; "enormous
           expenses"; "tremendous sweeping plains"; "a tremendous
           fact in human experience; that a whole civilization
           should be dependent on technology"- Walter Lippman; "a
           plane took off with a tremendous noise" [syn: enormous,
           tremendous]