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]