What is "reguluses"

Regulus \Reg"u*lus\ (-l?s), n.; pl. E. Reguluses (-?z), L. Reguli (-l?). [L., a petty king, prince, dim. of rex, regis, a king: cf. F. r['e]gule. See Regal.]

1. A petty king; a ruler of little power or consequence.

2. (Chem. & Metal.) The button, globule, or mass of metal, in a more or less impure state, which forms in the bottom of the crucible in smelting and reduction of ores.

   Note: The name was introduced by the alchemists, and applied by them in the first instance to antimony. It signifies little king; and from the facility with which antimony alloyed with gold, these empirical philosophers had great hopes that this metal, antimony, would lead them to the discovery of the philosopher's stone.
   --Ure.

3. (Astron.) A star of the first magnitude in the constellation Leo; -- called also the Lion's Heart.