rotor

American  

[roh-ter] / ˈroʊ tər /

noun

1. Electricity. a rotating member of a machine.

2. Aeronautics. a system of rotating airfoils, as the horizontal ones of a helicopter or of the compressor of a jet engine.

3. any of a number of tall, cylindrical devices mounted on a special ship rotor ship and rotated in such a way that the Magnus effect of wind impinging on the cylinders is used to drive and maneuver the vessel.

4. (in a self-winding watch) a weight eccentrically mounted on an arbor for keeping the mainspring wound.

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rotor British  

/ ˈrəʊtə /

noun

1. the rotating member of a machine or device, esp the armature of a motor or generator or the rotating assembly of a turbine Compare stator

2. a device having blades radiating from a central hub that is rotated to produce thrust to lift and propel a helicopter

3. the revolving arm of the distributor of an internal-combustion engine

4. a violent rolling wave of air occurring in the lee of a mountain or hill, in which the air rotates about a horizontal axis

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Etymology

Origin of rotor

First recorded in 1873; short for rotator

Example Sentences

One lowly bacterium possesses a flagellum—a tiny tail or rotor.

From The Wall Street Journal • Apr. 16, 2026

The company said some ships were even being built "rotor ready".

From BBC • Oct. 13, 2025

A tweet about Tuesday’s announcement included a video showing a spinning wheel with a Tesla logo that could have been the rotor of a Tesla eVTOL, or quadcopter drone.

From Barron's • Oct. 7, 2025

It appeared that the helicopter augered into the dirt embankment on the side of the highway, tearing up weeds with its tail rotor before skidding across five freeway lanes.

From Los Angeles Times • Oct. 7, 2025

Turing sets his rotor into an open slot.

From "The Bletchley Riddle" by Ruta Sepetys and Steve Sheinkin