noun a rare earth, regarded by some as an oxide of the supposed element gadolinium, by others as only a mixture of the oxides of yttrium, erbium, ytterbium, ·etc.
2. gadolinia ·add. ·noun a rare earth associated with yttria and regarded as the oxide (gd2o3) of a metallic element, gad`o*lin"i*um (/), with an assigned atomic weight of 153.3.