The Collaborative International Dictionary of English v.0.48:

Calypso \Ca*lyp"so\ (k[.a]*l[i^]p"s[-o]), n. [The Latinized
   Greek name of a beautiful nymph.] (Bot.)
   A small and beautiful species of orchid, having a flower
   variegated with purple, pink, and yellow. It grows in cold
   and wet localities in the northern part of the United States.
   The Calypso borealis is the only orchid which reaches
   68[deg] N.
   [1913 Webster]

WordNet (r) 3.0 (2006):

calypso
    n 1: rare north temperate bog orchid bearing a solitary white to
         pink flower marked with purple at the tip of an erect
         reddish stalk above 1 basal leaf [syn: calypso, fairy-
         slipper, Calypso bulbosa]
    2: (Greek mythology) the sea nymph who detained Odysseus for
       seven years