a soft, silver-gray, ductile chemical element, one of the rare-earth elements, found in gadolinite and other minerals: symbol, Tb; at. no., 65
ModL: so named (1843) by Mosander, its discoverer, after Ytterby: see erbium
See terbium in American Heritage Dictionary 4
noun Symbol Tb
A soft, silvery-gray metallic rare-earth element, used in x-ray and color television tubes. Atomic number 65; atomic weight 158.925; melting point 1,356°C; boiling point 3,123°C; specific gravity 8.229; valence 3, 4. See Table at element.