The Collaborative International Dictionary of English v.0.48:

patina \pat"ina\ (p[a^]t"[i^]*n[.a]; It. p[aum]"t[-e]*n[.a]), n.
   [It., fr. L. patina a dish, a pan, a kind of cake. Cf.
   Paten.]
   1. A dish or plate of metal or earthenware; a patella.
      [1913 Webster]

   2. (Fine Arts) The color or incrustation which age gives to
      works of art; especially, the green rust which covers
      ancient bronzes, coins, and medals. --Fairholt.
      [1913 Webster]

WordNet (r) 3.0 (2006):

patina
    n 1: a fine coating of oxide on the surface of a metal