Source : Webster's Revised Unabridged Dictionary (1913)

Lady's slipper \La"dy's slip"per\ (Bot.)
   Any orchidaceous plant of the genus {Cypripedium}, the
   labellum of which resembles a slipper. Less commonly, in the
   United States, the garden balsam ({Impatiens Balsamina}).

Source : WordNet®

lady's slipper
     n : any of several chiefly American wildflowers having an
         inflated pouchlike lip; difficult or impossible to
         cultivate in the garden [syn: {lady-slipper}, {ladies'
         slipper}, {slipper orchid}]