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Webster's Dictionary (1865)

Rēg'ū-lūs, n.

noun

n.; Eng. pl. RĒG'Ū-LŪS-ĒS; Lat. pl. RĒG'Ū-LĪ. [Lat., a petty king, prince, dim. of rex, regis, a king; Fr. régule, Sp. régulo, It. regolo.]

  1. A petty king; a ruler of little power or consequence.
  2. (Chem.) The pure metal, which, in the melting of ores, falls to the bottom of the crucible; as, regulus of antimony.
  3. (Astron.) A star of the first magnitude in the constellation Leo;—called also the Lion’s Heart.