chlorous \chlo"rous\, a. see chlorine.
   1. of, pertaining to, or derived from, chlorine; -- said of
      those compounds of chlorine in which this element has a
      valence of three, the next lower than in chloric
      compounds; as, chlorous acid, hclo2.
      1913 webster

   2. chem. physics pertaining to, or resembling, the
      electro-negative character of chlorine; hence,
      electro-negative; -- opposed to basylous or zincous.
      obs.
      1913 webster
see also:
chlorine hclo2