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primum mobile

(prī′məm mō′bə lē′)

Astron. in the Ptolemaic system, the tenth and outermost concentric sphere, revolving from east to west around the earth and causing all celestial bodies to revolve with it

Origin: ML, first movable thing: see prime, & mobile

See primum mobile in American Heritage Dictionary 4

noun

The tenth and outermost concentric sphere of the universe thought in Ptolemaic astronomy to revolve around the earth from east to west in 24 hours and believed to cause the other nine spheres to revolve with it.
See prime mover.

Origin:

Origin: Medieval Latin prīmum mōbile

Origin: : prīmum

Origin: , neuter of prīmus, first

Origin: + mōbile

Origin: , from neuter of mōbilis, movable (translation of Arabic al-muḥarrik al-’awwal : al-, the + muḥarrik, mover + ’awwal, first)