Source : Webster's Revised Unabridged Dictionary (1913)

Polyanthus \Pol`y*an"thus\, n.; pl. {Polyanthuses}. [NL., fr.
   Gr. ? rich in flowers; poly`s many + ? flower.] [Written also
   {polyanthos}.] (Bot.)
   (a) The oxlip. So called because the peduncle bears a
       many-flowered umbel. See {Oxlip}.
   (b) A bulbous flowering plant of the genus {Narcissus} ({N.
       Tazetta}, or {N. polyanthus} of some authors). See
       Illust. of {Narcissus}.

Source : WordNet®

polyanthus
     n : florists' primroses; considered a complex hybrid derived
         from oxlip, cowslip, and common primrose [syn: {Primula
         polyantha}]