Definition of regulus
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
Recent Examples of regulus from the Web
Regulus will be only three degrees away from the moon, about equal to the width of your two middle fingers held at arm’s length.
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Britannica.com: Encyclopedia article about regulus
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