The Collaborative International Dictionary of English v.0.48:

Oxlip \Ox"lip`\, n. [AS. oxanslyppe. See Ox, and Cowslip.]
   (Bot.)
   The great cowslip (Primula veris, var. elatior).
   [1913 Webster]

WordNet (r) 3.0 (2006):

oxlip
    n 1: Eurasian primrose with yellow flowers clustered in a one-
         sided umbel [syn: oxlip, paigle, Primula elatior]