a. [ L. nitrosus full of natron: cf. F. nitreux. See Niter. ] 1. Of, pertaining to, or containing, niter; of the quality of niter, or resembling it. [ 1913 Webster ]
2. (Chem.) Of, pertaining to, or designating, any one of those compounds in which nitrogen has a relatively lower valence as contrasted with nitric compounds. [ 1913 Webster ]
Nitrous acid (Chem.), a hypothetical acid of nitrogen HNO2, not known in the free state, but forming a well known series of salts, viz., the nitrites. -- Nitrous oxide. See Laughing gas. [ 1913 Webster ]