Source : Webster's Revised Unabridged Dictionary (1913)

Parnassia \Par*nas"si*a\, n. [NL.] (Bot.)
   A genus of herbs growing in wet places, and having white
   flowers; grass of Parnassus.

Source : WordNet®

parnassia
     n : 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: {grass-of-Parnassus}]