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castor

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

noun

  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.

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.

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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
castor 2 British  
/ ˈkɑːstə /

noun

  1. a variant spelling of caster caster

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
castor 3 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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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.

Etymology

Origin of castor1

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

Origin of Castor2

Named after Castor; Castor and Pollux

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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

From Los Angeles Times • Nov. 7, 2024

Ricin is a highly toxic poison naturally derived from castor oil plants.

From BBC • Oct. 29, 2024

The modified Arabidopsis overcame metabolic bottlenecks and produced significant amounts of an oil similar to castor oil that it doesn't naturally produce.

From Science Daily • Apr. 30, 2024

Other formulas are based on plant oils, including castor bean, cedarwood, clove and peppermint.

From Seattle Times • May 20, 2023

They burned a lot of fuel, and they used castor oil, which leaked and splattered all over the cockpit after a few flights.

From "A Thousand Sisters" by Elizabeth Wein

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.