Source : Webster's Revised Unabridged Dictionary (1913)

Pollux \Pol"lux\, n. [L., the twin brother of castor; also, the
   constellation.]
   1. (Astron.) A fixed star of the second magnitude, in the
      constellation Gemini. Cf. 3d {Castor}.

   2. (Min.) Same as {Pollucite}.

Source : WordNet®

Pollux
     n : the brightest star in Gemini; close to Castor