Regulus

noun

1. a multiple star, the brightest star in the constellation Leo: magnitude, 1.4
2. pl. reguluses or reguli Chem., Metallurgy
   1. 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