lady's slipper

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various orchids of the subfamily Cypripedioideae and especially the genus Cypripedium, having showy flowers with the lip modified into a slipperlike pouch.

from the GNU version of the Collaborative International Dictionary of English.

• noun (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).

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A variety of orchid in the subfamily Cypripedioideae distinguished by their slipper-shaped pouches which trap insects to improve pollination rates.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of several chiefly American wildflowers having an inflated pouchlike lip; difficult or impossible to cultivate in the garden