The Collaborative International Dictionary
Osmious
Osmious \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.
Wiktionary
osmious
a. (context chemistry English) Denoting those compounds of osmium in which the element has a valence relatively lower than in the osmic compounds. alt. (context chemistry English) Denoting those compounds of osmium in which the element has a valence relatively lower than in the osmic compounds.