primum mobile

noun pri·mum mo·bi·le \ˈprī-məm-ˈmō-bə-lē, ˈprē-\

plural primum mobiles

Definition of PRIMUM MOBILE

: the outermost concentric sphere conceived in medieval astronomy as carrying the spheres of the fixed stars and the planets in its daily revolution

Middle English, from Medieval Latin, literally, first moving thing

First Known Use: 15th century

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