noun

1. a multiple star, the brightest star in the constellation Leo: magnitude, 1.4
2. pl. reguluses -·luses or reguli -·li′ (-lī′)Chem., Metallurgy

   1. Etymology: because of its ready combination with gold, the “king of metals”

      metallic antimony
      in full regulus of antimony
   2. impure metal produced by the smelting or reduction of various ores
   3. partly purified metal that sinks to the bottom of a crucible or furnace in smelting

Etymology: ModL < L, dim. of rex, a king: see right