[rare earth] n (1875) 1: any of a group of similar oxides of metals or a mixture of such oxides occurring together in widely distributed but relatively scarce minerals
2: rare earth element
[rare earth] n (1875) 1: any of a group of similar oxides of metals or a mixture of such oxides occurring together in widely distributed but relatively scarce minerals
2: rare earth element
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012