D defs.my
Entry 2 senses Webster, 1913

nitro-

· ni·tro- · IPA
01 pref. A combining form or an adjective denoting the presence of niter.
  1. 1.
    A combining form or an adjective denoting the presence of niter.
  2. 2.
    A combining form (used also adjectively) designating certain compounds of nitrogen or of its acids; as nitrohydrochloric, nitrocalcite; also, designating the group or radical NO2, or its compounds, as nitrobenzene (C6H5.NO2).(Chem.)
Phrases & compounds
Nitro group — the radical NO2; -- called also nitroxyl.