Source : Webster's Revised Unabridged Dictionary (1913)

Isonitroso- \I`so*ni*tro"so-\ [Iso- + nitroso-.] (Chem.)
   A combining from (also used adjectively), signifying:
   Pertaining to, or designating, the characteristic,
   nitrogenous radical, {NOH}, called the isonitroso group.