The Collaborative International Dictionary of English v.0.48:

Metallic \Me*tal"lic\, a. [L. metallicus, fr. metallum: cf. F.
   m['e]tallique. See Metal.]
   1. Of or pertaining to a metal; of the nature of metal;
      resembling metal; as, a metallic appearance; a metallic
      alloy.
      [1913 Webster]

   2. (Chem.) Of, pertaining to, or characterized by, the
      essential and implied properties of a metal, as contrasted
      with a nonmetal or metalloid; conductive of electricity;
      basic; forming positive ions in solution; antacid.
      [1913 Webster +PJC]

   Metallic iron, iron in the state of the metal, as
      distinquished from its ores, as magnetic iron.

   Metallic paper, paper covered with a thin solution of lime,
      whiting, and size. When written upon with a pewter or
      brass pencil, the lines can hardly be effaced.

   Metallic tinking (Med.), a sound heard in the chest, when a
      cavity communicating with the air passages contains both
      air and liquid.
      [1913 Webster]

WordNet (r) 3.0 (2006):

metallic
    adj 1: containing or made of or resembling or characteristic of
           a metal; "a metallic compound"; "metallic luster"; "the
           strange metallic note of the meadow lark, suggesting the
           clash of vibrant blades"- Ambrose Bierce [syn:
           metallic, metal(a)] [ant: nonmetal, nonmetallic]
    n 1: a fabric made of a yarn that is partly or entirely of metal
    2: a yarn made partly or entirely of metal

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "metallic":
   brassy, brazen, choked, coarse, cracked, croaking, croaky, dry,
   gruff, guttural, harsh, harsh-sounding, hoarse, husky, metal,
   metallike, metalline, metalloid, organometallic, ragged, raucid,
   raucous, rough, roupy, rude, squawking, squawky, stertorous,
   strangled, thick, throaty, tinny