The Collaborative International Dictionary of English v.0.48:

Trigenic \Tri*gen"ic\, a. [Pref. tri- + gen- + -ic. So named in
   reference to its composition, it being supposed to contain
   the radicals of three molecules of cyanic acid.] (Chem.)
   Of, pertaining to, or designating, an acid, C4H7N3O2,
   obtained, by the action of the vapor of cyanic acid on cold
   aldehyde, as a white crystalline substance having a slightly
   acid taste and faint smell; -- called also ethidene-biuret
   or ethylidene-biuret.
   [1913 Webster]