1. a suffix forming adjectives that have the general sense "possessing, full of" a given quality ( covetous; glorious; nervous; wondrous ); -ous and its variant -ious have often been used to Anglicize Latin adjectives with terminations that cannot be directly adapted into English ( atrocious; contiguous; garrulous; obvious; stupendous ). As an adjective-forming suffix of neutral value, it regularly Anglicizes Greek and Latin adjectives derived without suffix from nouns and verbs; many such formations are productive combining forms in English, sometimes with a corresponding nominal combining form that has no suffix; cf. -fer, -ferous; -phore, -phorous; -pter, -pterous; -vore, -vorous .
2. a suffix forming adjectival correspondents to the names of chemical elements; specialized, in opposition to like adjectives ending in -ic , to mean the lower of two possible valences ( stannous chloride, SnCl 2 , and stannic chloride SnCl 4 ).
[ ME -osus; a doublet of -OSE 1 ]