Os"mi*ous (?), a. (Chem.)
Denoting those compounds of osmium in which the element has a
valence relatively lower than in the osmic compounds; as,
osmious chloride. [Written also osmous.]
Osmious acid (Chem.), an acid derived
from osmium, analogous to sulphurous acid, and forming unstable
salts. It is a brown amorphous substance.