The Collaborative International Dictionary of English v.0.48:

Primrose \Prim"rose`\, n. [OE. primerole, F. primerole, a
   derivative fr. LL. primula, from L. primus first. See
   Prime, a.] (Bot.)
   (a) An early flowering plant of the genus Primula (Primula
       vulgaris) closely allied to the cowslip. There are
       several varieties, as the white-, the red-, the
       yellow-flowered, etc. Formerly called also primerole,
       primerolles.
   (b) Any plant of the genus Primula.
       [1913 Webster]

   Evening primrose, an erect biennial herb (Enothera
      biennis), with yellow vespertine flowers, common in the
      United States. The name is sometimes extended to other
      species of the same genus.

   Primrose peerless, the two-flowered Narcissus (Narcissus
      biflorus). [Obs.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

Primula vulgaris
    n 1: plant of western and southern Europe widely cultivated for
         its pale yellow flowers [syn: English primrose, Primula
         vulgaris]