castor

• (Received Pronunciation) IPA^(key): /ˈkɑːs.tə/

• Audio (Southern England):

  (file)

• (General American) IPA^(key): /ˈkæs.tɚ/
• Rhymes: -ɑːstə(ɹ), -æstə(ɹ)
• Homophone: caster

From Middle French castor, from Old French castor (“beaver”), from Latin castor (“beaver”), from Ancient Greek κάστωρ (kástōr), from Doric Greek κάστον (káston, “wood”).

castor (countable and uncountable, plural castors)

1. A hat made from the fur of the beaver.
   • 1826, [Walter Scott], chapter V, in Woodstock; Or, The Cavalier. […], volume I, Edinburgh: […] [James Ballantyne and Co.] for Archibald Constable and Co.; London: Longman, Rees, Orme, Brown, and Green, →OCLC, page 135:

     I have been always noted for the jaunty manner in which I wear my castor— […]

2. A heavy quality of broadcloth for overcoats.
3. Castoreum (bitter exudate of mature beavers).
4. Any of various nymphalid butterflies of the genus Ariadne, of Africa and Asia.

• (hat): beaver, castoreum (archaic)
• (cloth): beaver

• castorette
• castoreum

Named from Greek mythology; see Castor and Pollux. The name pollux was given to another mineral with which it was always found.

castor (uncountable)

1. (mineralogy) A variety of petalite found in Elba.

• castorite

Alternative spelling of caster, via cast +‎ -or (the Latinate varient of -er).

castor (plural castors)

1. (especially UK) Alternative spelling of caster, especially in its senses
   1. A pivoting roller attached to the bottom of furniture to allow it to be moved.
   2. A container with a perforated cap for sprinkling its contents, especially salt, pepper, etc.
      • 1851 November 14, Herman Melville, “The Ramadan”, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley, →OCLC, page 92:

        Mrs. Hussey soon appeared, with a mustard-pot in one hand and a vinegar-cruet in the other, having just broken away from the occupation of attending to the castors, and scolding her little black boy meantime.

• castor sugar
• castored
• castoring

“castor”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.

• Castro, Cators, Croats, acrost, actors, co-star, costar, scroat, scrota, tarocs

castor m (plural castores)

1. beaver

Borrowed from Latin castŏrem.

• IPA^(key): (Central, Balearic) [kəsˈto]
• IPA^(key): (Valencia) [kasˈtoɾ]

• Audio (Valencia):

  (file)

castor m (plural castors)

1. beaver

• “castor”, in Diccionari de la llengua catalana [Dictionary of the Catalan Language] (in Catalan), second edition, Institute of Catalan Studies [Catalan: Institut d'Estudis Catalans], April 2007

Inherited from Middle French castor, from Old French castor, borrowed from Latin castor, itself from Ancient Greek κάστωρ (kástōr). Though borrowed into French early on, the word remained a more learned term at first, while bièvre was the popular synonym.

• IPA^(key): /kas.tɔʁ/

• Audio:

  (file)

• Audio (Paris):

  (file)

• Homophone: castors

castor m (plural castors)

1. beaver (aquatic mammal)

   Synonym: (archaic) bièvre

• “castor”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.

• scorât

From Latin castor (“beaver”).

• IPA^(key): /kasˈtoɾ/

castor m (plural castores)

1. beaver

   Synonym: befre

• “castor”, in Dicionario da Real Academia Galega (in Galician), A Coruña: Royal Galician Academy, 2012–2025

From Ancient Greek κάστωρ (kástōr), from Doric Greek κάστον (káston, “wood”). See also Sanskrit कस्तूरी (kastūrī, “musk”).

• (Classical Latin) IPA^(key): [ˈkas.tɔr]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈkas.t̪or]

castor m (genitive castoris); third declension

1. beaver

Third-declension noun.

• fiber, beber (Late Latin)

• castoreātus
• castoreum
• castorīnātus
• castorīnus

• Castor

• Castor

• “castor”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• “castor”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
• "castor", in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• castor in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
• “castor”, in Harry Thurston Peck, editor (1898), Harper’s Dictionary of Classical Antiquities, New York: Harper & Brothers
• “castor”, in William Smith, editor (1848), A Dictionary of Greek and Roman Biography and Mythology, London: John Murray

• Arctos

Borrowed from French castor, from Latin castor (“beaver”).

castor m (plural castors)

1. (Jersey) beaver

Learned borrowing from Latin castōrem (“beaver”), from Ancient Greek κάστωρ (kástōr).

• Rhymes: -oɾ
• Hyphenation: cas‧tor

castor m (plural castores)

1. beaver (Castor sp.)
2. fur of a beaver
3. castor (a hat made from the fur of the beaver)

• “castor” in Dicionário Aberto based on Novo Diccionário da Língua Portuguesa de Cândido de Figueiredo, 1913
• “castor”, in Michaelis Dicionário Brasileiro da Língua Portuguesa (in Portuguese), São Paulo: Editora Melhoramentos, 2015–2025
• “castor”, in Dicionário Priberam da Língua Portuguesa (in Portuguese), Lisbon: Priberam, 2008–2025

Borrowed from French castor and its source, Latin castor, from Ancient Greek κάστωρ (kástōr).

castor m (plural castori)

1. beaver

   Synonyms: breb (“European beaver”); (less common) biber

• “castor”, in DEX online—Dicționare ale limbii române (Dictionaries of the Romanian language) (in Romanian), 2004–2025

From Latin castor (“beaver”).

• IPA^(key): /kasˈtoɾ/ [kasˈt̪oɾ]

• Audio (Colombia):

  (file)

• Rhymes: -oɾ
• Syllabification: cas‧tor

castor m (plural castores)

1. beaver

• “castor”, in Diccionario de la lengua española [Dictionary of the Spanish Language] (in Spanish), online version 23.8, Royal Spanish Academy [Spanish: Real Academia Española], 10 December 2024