Cas"tor (?), n. [L. castor the beaver, Gr. &?;; of uncertain origin.] 1. (Zoöl.) A genus of rodents, including the beaver. See Beaver.

2. Castoreum. See Castoreum.

3. A hat, esp. one made of beaver fur; a beaver.

I have always been known for the jaunty manner in which I wear my castor.
Sir W. Scott.

4. A heavy quality of broadcloth for overcoats.

Cast"or (?), n. See Caster, a small wheel.

Cas"tor (?), n. [L.] (Astron.) the northernmost of the two bright stars in the constellation Gemini, the other being Pollux.

{ Cas"tor, Cas"tor*ite (?), } n. [The minerals castor and pollux were so named because found together on the island of Elba. See Castor and Pollux.] (Min.) A variety of the mineral called petalite, from Elba.

• a pivoting roller attached to the bottom of furniture to allow it to be moved
  
• a hat made from the fur of the beaver
  
• (in Greek mythology) one of the Dioscuri
  
• (astronomy) a double star in the constellation Gemini
  
  Spanish
• beaver