rare earth ra·reearth uncommon noun 1. any element of the lanthanide series (atomic numbers 57 through 71) Synonymsrare earthrare-earth elementlanthanoidlanthanidelanthanon Related words Word family rare-earth element Broader terms group Narrower terms terbium metal WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
