Nitrous

a.
  1. Of, pertaining to, or containing, niter; of the quality of niter, or resembling it.
  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.
    3. 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.