A combining form or an adjective denoting the presence of niter. [1913 Webster]
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). [1913 Webster]
Nitro group, the radical NO2; -- called also nitroxyl.
Nitro-, comb. form 1 of or containing nitric acid, nitre, or nitrogen.
2 made with or by use of any of these.
3 of or containing the monovalent -NO2 group (the nitro groups in TNT).