Source : Webster's Revised Unabridged Dictionary (1913)

Cepheus \Ce"pheus\, n. (Astron.)
   A northern constellation near the pole. Its head, which is in
   the Milky Way, is marked by a triangle formed by three stars
   of the fourth magnitude. See {Cassiopeia}.

Source : WordNet®

Cepheus
     n : a faint constellation in the northern hemisphere near
         Cassiopeia and the pole star