The Collaborative International Dictionary of English v.0.48:

Colleen \Col*leen"\, n. [Ir. cailin.]
   A girl; a maiden. [Anglo-Irish]

         Of all the colleens in the land
         Sweet Mollie is the daisy.               --The Century.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

colleen
    n 1: an Irish girl