Cassiopeia \Cas`si*o*pe"ia\, n. [NL., fr. Gr. ?.] (Astron.) A constellation of the northern hemisphere, situated between Cepheus and Perseus; -- so called in honor of the wife of Cepheus, a fabulous king of Ethiopia. {Cassiopeia's Chair}, a group of six stars, in Cassiopeia, somewhat resembling a chair.