The Collaborative International Dictionary of English v.0.48:

Luna \Lu"na\, n. [L.; akin to lucere to shine. See Light, n.,
   and cf. Lune.]
   1. The moon.
      [1913 Webster]

   2. (Alchemy) Silver.
      [1913 Webster]

   Luna cornea (Old Chem.), horn silver, or fused silver
      chloride, a tough, brown, translucent mass; -- so called
      from its resemblance to horn.

   Luna moth (Zool.), a very large and beautiful American moth
      (Actias luna). Its wings are delicate light green, with
      a stripe of purple along the front edge of the anterior
      wings, the other margins being edged with pale yellow.
      Each wing has a lunate spot surrounded by rings of light
      yellow, blue, and black. The caterpillar commonly feeds on
      the hickory, sassafras, and maple.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Actias luna
    n 1: large pale-green American moth with long-tailed hind wings
         and a yellow crescent-shaped mark on each forewing [syn:
         luna moth, Actias luna]