The Collaborative International Dictionary of English v.0.48:

Trisnitrate \Tris*ni"trate\, n. [Gr. ? thrice + E. nitrate.]
   (Chem.)
   A nitrate formed from three molecules of nitric acid; also,
   less properly, applied to certain basic nitrates; as,
   trisnitrate of bismuth.
   [1913 Webster]