The Collaborative International Dictionary of English v.0.48:

Cosmic \Cos"mic\ (k?z"m?k), Cosmical \Cos"mic*al\ (-m?-kal), a.
   [Gr. kosmiko`s of the world, fr. ko`smos: cf. F. cosmique.
   See Cosmos.]
   1. Pertaining to the universe, and having special reference
      to universal law or order, or to the one grand harmonious
      system of things; hence; harmonious; orderly.
      [1913 Webster]

   2. Pertaining to the solar system as a whole, and not to the
      earth alone.
      [1913 Webster]

   3. Characteristic of the cosmos or universe; inconceivably
      great; vast; as, cosmic speed. "Cosmic ranges of time."
      --Tyndall.
      [1913 Webster]

   4. (Astron.) Rising or setting with the sun; -- the opposite
      of acronycal.
      [1913 Webster]

   5. of unsurpassed size, extent, or significance; vast; as, of
      cosmic proportions; of cosmic importance.
      [PJC]

WordNet (r) 3.0 (2006):

cosmic
    adj 1: of or from or pertaining to or characteristic of the
           cosmos or universe; "cosmic laws"; "cosmic catastrophe";
           "cosmic rays"
    2: inconceivably extended in space or time

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "cosmic":
   Gargantuan, amplitudinous, astronomical, awesome, boundless, bulky,
   colossal, cosmogonal, cosmogonic, cosmologic, enormous, extensive,
   galactic, gigantic, huge, immeasurable, immense, infinite,
   king-size, large, mammoth, massive, massy, monster, monstrous,
   monumental, mountainous, outsize, overgrown, prodigious, sizable,
   spacious, stupendous, titanic, tremendous, universal, vast,
   voluminous, weighty