Hy`po*ni"trous (?), a. [Pref. hypo- + nitrous.] Chem.
Containing or derived from nitrogen having a lower valence than in nitrous compounds.
Hyponitrous acid Chem., an unstable nitrogen acid, NOH, whose salts are produced by reduction of the nitrates, although the acid itself is not isolated in the free state except as a solution in water; -- called also nitrosylic acid.
© Webster 1913.