prime mover

noun

1

a

: an initial source of motive power (such as a windmill, waterwheel, turbine, or internal combustion engine) designed to receive and modify force and motion as supplied by some natural source and apply them to drive machinery

b

: a powerful tractor or truck usually with all-wheel drive

2

: the self-moved being that is the source of all motion

3

: the original or most effective force in an undertaking or work

education is … a prime mover of cultural and societal change

—R. C. Buck

Examples of prime mover in a Sentence

She was the prime mover behind the town's annual summer festival.

Recent Examples on the Web

While many traditional inner-thigh exercises focus solely on squeezing motions, more effective adductor training also incorporates movements in multiple planes and challenges the muscles to work as stabilizers rather than just prime movers. —Dana Santas, CNN Money, 26 Sep. 2025

As much as Putin, Trump has been the prime mover behind these changes, which might prompt Europe to fully break with Washington. —Michael Kimmage, Foreign Affairs, 19 Aug. 2025

Compared with diesels, electric prime movers are very expensive, don’t go far on a charge, and take a long time to recharge. —Ian Baker july 22, New Atlas, 22 July 2025

The retrofit process involved removing the original hood and prime mover—the large diesel engine and generator that traditionally power the locomotive—leaving behind a long, open deck and the existing operator cab. —David Blekhman, Forbes.com, 17 July 2025

Word History

Etymology

(sense 2) translation of Medieval Latin prīmum mōbile, prīmus mōtus, prīmus mōtor or other variants

Note: See also etymology at primum mobile.

First Known Use

1795, in the meaning defined at sense 1a

Rhymes for prime mover

• approver
• improver
• maneuver
• remover
• louver

Medical Definition

prime mover

noun

ˈprīm-ˈmü-vər 

: agonist sense 1