The Collaborative International Dictionary of English v.0.48:
Parnassia \Par*nas"si*a\, n. [NL.] (Bot.) A genus of herbs growing in wet places, and having white flowers; grass of Parnassus. [1913 Webster]WordNet (r) 3.0 (2006):
parnassia n 1: any of various usually evergreen bog plants of the genus Parnassia having broad smooth basal leaves and a single pale flower resembling a buttercup [syn: parnassia, grass-of-Parnassus]