nitro- \ni"tro-\pref.
   1. A combining form or an adjective denoting the presence of
      niter.
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   2. (Chem.) 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).
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   Nitro group, the radical NO2; -- called also nitroxyl.
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Nitroxyl \Ni*trox"yl\, n. [Nitro- + oxygen + -yl.] (Chem.)
   The group -NO2, usually called the nitro group.
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