The Collaborative International Dictionary of English v.0.48:

Monotropa \Mo*not"ro*pa\, n. [NL., fr. Gr. mo`nos single + ?
   turn, from ? to turn.] (Bot.)
   A genus of parasitic or saprophytic plants including the
   Indian pipe and pine sap. The name alludes to the dropping
   end of the stem.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Monotropa
    n 1: leafless fleshy saprophytic plants; in some classifications
         placed in the family Pyrolaceae [syn: Monotropa, genus
         Monotropa]