Source : Webster's Revised Unabridged Dictionary (1913)

Diazo- \Di*az"o-\ [Pref. di- + azo-] (Chem.)
   A combining form (also used adjectively), meaning pertaining
   to, or derived from, a series of compounds containing a
   radical of two nitrogen atoms, united usually to an aromatic
   radical; as, diazo-benzene, {C6H5.N2.OH}.

   Note: Diazo compounds are in general unstable, but are of
         great importance in recent organic chemistry. They are
         obtained by a partial reduction of the salts of certain
         amido compounds.

   {Diazo reactions} (Chem.), a series of reactions whereby
      diazo compounds are employed in substitution. These
      reactions are of great importance in organic chemistry.