ruthenium, n. [NL. So named from the Ruthenians, a Little Russian people, as coming from Russia, the metal having been found in the Ural mountains.].
A rare element of the light platinum group, found associated with platinum ores, and isolated as a hard, brittle steel-gray metal which is very infusible. Symbol Ru. Atomic weight 103.5. Specific gravity 12.26. See Platinum metals, under Platinum. [1913 Webster]