The Collaborative International Dictionary of English v.0.48:

Biuret \Bi"u*ret\, n. [Pref. bi- + urea.] (Chem.)
   A white, crystalline, nitrogenous substance, C2O2N3H5,
   formed by heating urea. It is intermediate between urea and
   cyanuric acid.
   [1913 Webster]