The Collaborative International Dictionary of English v.0.48:

Galactic \Ga*lac"tic\, a. [Gr. ? milky, fr. ?, ?, milk. See
   Galaxy, and cf. Lactic.]
   1. Of or pertaining to milk; got from milk; as, galactic
      acid.
      [1913 Webster]

   2. Of or pertaining to the galaxy or Milky Way.
      [1913 Webster]

   Galactic circle (Astron.), the great circle of the heavens,
      to which the course of the galaxy most nearly conforms.
      --Herschel.

   Galactic poles, the poles of the galactic circle.
      [1913 Webster]

WordNet (r) 3.0 (2006):

galactic
    adj 1: of or relating to a galaxy (especially our galaxy the
           Milky Way); "the galactic plane"
    2: inconceivably large [syn: astronomic, astronomical,
       galactic]

Moby Thesaurus II by Grady Ward, 1.0:

106 Moby Thesaurus words for "galactic":
   Cynthian, Gargantuan, all-comprehending, all-comprehensive,
   all-covering, all-embracing, all-encompassing, all-filling,
   all-including, all-inclusive, all-pervading, allover,
   amplitudinous, anagalactic, asteroidal, astral, astrologic,
   astrologistic, astrologous, astronomic, astronomical,
   astrophysical, awesome, boundless, bulky, catholic, celestial,
   circumplanetary, cislunar, colossal, cosmic, cosmopolitan,
   country-wide, ecumenic, empyreal, empyrean, enormous, equinoctial,
   extensive, extragalactic, gigantic, global, heaven-wide, heavenly,
   heliacal, huge, immeasurable, immense, infinite, intercosmic,
   international, interplanetary, intersidereal, interstellar,
   king-size, large, lunar, lunary, lunate, lunular, lunulate,
   mammoth, massive, massy, meteoric, meteoritic, monster, monstrous,
   monumental, mountainous, national, nebular, nebulose, nebulous,
   nondenominational, nonsectarian, outsize, overgrown, planetal,
   planetarian, planetary, planetesimal, prodigious, semilunar,
   sidereal, sizable, solar, spacious, sphery, star-spangled,
   star-studded, starry, stellar, stellary, stupendous, terrestrial,
   titanic, total, tremendous, universal, uranic, vast, voluminous,
   weighty, world-wide, zodiacal