Main Entry: reg·u·lus

Pronunciation: \ˈre-gyə-ləs\

Function: noun

Etymology: New Latin, from Latin, petty king, from reg-, rex king — more at royal

Date: 1559

1 capitalized : a first-magnitude star in the constellation Leo
2 [Medieval Latin, metallic antimony, from Latin] : the more or less impure mass of metal formed beneath the slag in smelting and reducing ores