D defs.my
Entry 2 senses Webster, 1913

Nitrous

/nĭt'-rəs/ · Ni·trous · IPA /ˈnaɪtɹəs/
01 a. Of, pertaining to, or containing, niter; of the quality of niter, or resembling it.
  1. 1.
    Of, pertaining to, or containing, niter; of the quality of niter, or resembling it.
  2. 2.
    Of, pertaining to, or designating, any one of those compounds in which nitrogen has a relatively lower valence as contrasted with nitric compounds.(Chem.)
Phrases & compounds
Nitrous acid — 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.