The Collaborative International Dictionary of English v.0.48:

Nitrate \Ni"trate\, n. [Cf. F. nitrate.] (Chem.)
   A salt of nitric acid.
   [1913 Webster]

   Nitrate of silver, a white crystalline salt (AgNO3), used
      in photography and as a cauterizing agent; -- called also
      lunar caustic, and more commonly called silver
      nitrate.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

silver nitrate
    n 1: a nitrate used in making photographic emulsions; also used
         in medicine as a cautery and as a topical antibacterial
         agent