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• castor
  castor

  noun

  Also a brownish, unctuous substance with a strong, penetrating odor, secreted by certain glands in the groin of the beaver, used in medicine and perfumery.
• Castor
  Castor

  noun

  a star of the second magnitude in the constellation Gemini, the more northerly of the two bright stars in this constellation.

castor

¹ American  

[kas-ter, kah-ster] / ˈkæs tər, ˈkɑ stər /

noun

• castors
  plural

1. Also a brownish, unctuous substance with a strong, penetrating odor, secreted by certain glands in the groin of the beaver, used in medicine and perfumery.

2. a hat made of beaver or rabbit fur.

3. a heavy woolen cloth used mainly for coats.

4. a beaver.

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Castor ² American  

[kas-ter, kah-ster] / ˈkæs tər, ˈkɑ stər /

noun

Astronomy.

1. a star of the second magnitude in the constellation Gemini, the more northerly of the two bright stars in this constellation.

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Castor ¹ British  

/ ˈkɑːstə /

noun

1. the second brightest star, Alpha Geminorum, in the constellation Gemini: a multiple star consisting of six components lying close to the star Pollux. Distance: 52 light years

2. classical myth See Castor and Pollux

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castor ² British  

/ ˈkɑːstə /

noun

1. the brownish aromatic secretion of the anal glands of a beaver, used in perfumery and medicine

2. the fur of the beaver

3. a hat made of beaver or similar fur

4. a less common name for beaver 1

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castor ³ British  

/ ˈkɑːstə /

noun

1. a variant spelling of caster caster

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Castor Scientific  

/ kăs′tər /

1. A bright multiple star in the constellation Gemini, with a combined apparent magnitude of 0.08. Scientific name: Alpha Geminorum.

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Other Word Forms

Noun Inflected Forms

• castors
  plural

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Etymology

Origin of castor¹

1350–1400; Middle English < Latin < Greek kástōr beaver

Origin of Castor²

Named after Castor; see Castor and Pollux

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Example Sentences

See Examples For:

castor Castor castors

Ricin, a highly toxic chemical, is a poison found naturally in castor beans.

From BBC ● Mar. 31, 2026

“Those, over there, are actually castor bean stalks,” Kleckner said as we zoomed past.

From Los Angeles Times ● Nov. 7, 2024

Those oils could replace the reliance of growing dangerous crops, like castor.

From Science Daily ● Apr. 30, 2024

Look for products that contain petroleum jelly, castor oil and glycerin, Rogers said.

From Seattle Times ● Feb. 5, 2024

My stomach hurt as if my mother had dosed me with castor oil.

From "The Lions of Little Rock" by Kristin Levine

Castor cited what she described as reckless attacks on other renewable-energy projects—such as wind power—and the independence of the NRC.

From The Wall Street Journal ● Jan. 8, 2026

Tampa Mayor Jane Castor called the incident "devastating" in a statement on X.

From BBC ● Nov. 8, 2025

Finally Castor canadensis, long maligned as a pest, is getting a rebrand as an ecological hero.

From Los Angeles Times ● Jan. 7, 2025

"I’ve said many times that if you want to pick a fight with Mother Nature, she’s winning 100 percent of the time," Tampa Mayor Jane Castor said in a press conference Tuesday.

From Salon ● Oct. 9, 2024

The fairest woman in the world was Helen, the daughter of Zeus and Leda and the sister of Castor and Pollux.

From "Mythology: Timeless Tales of Gods and Heroes" by Edith Hamilton

As for the metallic pepperpot-shaped aliens, created by designer Raymond Cusick, Ms Webb remembers rehearsals with actors "trolleying" around on castors in just the bottom halves of the characters that would become The Doctor's nemesis.

From BBC ● Dec. 21, 2023

It's odd at first; Stewart seems dazed by the noisiness of the production, to be moving as if on castors.

From Los Angeles Times ● Nov. 4, 2016

The sculptural giltwood pedestal includes leopard masks above three paw feet that conceal recessed brass castors.

From Architectural Digest ● Jan. 14, 2015

The blocks and castors terminating the legs are modern replacements and, like the French set, they are neither glamorous enough to satisfy buyers looking for trophies nor sought after as furniture to live with.

From New York Times ● Jul. 22, 2011

The chair for his sitters was raised eighteen inches from the floor, and turned round on castors.

From Six Centuries of Painting by Randall Davies

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