Late Middle English. From classical Latin radiōsus radiant, resplendent (Plautus), in post-classical Latin also radial, of or belonging to the radius of a circle or sphere, surrounded by rays of light, rayed from radius + -ōsus.
Definition of radious in US English:
radious
adjectiveˈreɪdɪəs
Radiant, bright. Now rare.
Origin
Late Middle English. From classical Latin radiōsus radiant, resplendent (Plautus), in post-classical Latin also radial, of or belonging to the radius of a circle or sphere, surrounded by rays of light, rayed from radius + -ōsus.