Entry 2 senses Webster, 1913 Pollux /päl'-əks/ · Pol·lux · IPA /pˈɑləks/ 01 n. A fixed star of the second magnitude, in the constellation Gemini. Cf. 3d Castor. 1. A fixed star of the second magnitude, in the constellation Gemini. Cf. 3d Castor.(Astron.) See: Castor 2. Same as Pollucite.(Min.) See: Pollucite