Source : Webster's Revised Unabridged Dictionary (1913)

Argentous \Ar*gen"tous\, a. (Chem.)
   Of, pertaining to, or containing, silver; -- said of certain
   silver compounds in which silver has a higher proportion than
   in argentic compounds; as, argentous chloride.

Source : WordNet®

argentous
     adj : relating to compounds in which silver is univalent