The Collaborative International Dictionary of English v.0.48:

Pipsissewa \Pip*sis"se*wa\, n. [From American Indian.] (Bot.)
   A low evergreen plant (Chimaphila umbellata), with narrow,
   wedge-lanceolate leaves, and an umbel of pretty nodding
   fragrant blossoms. It has been used in nephritic diseases.
   Called also prince's pine.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Chimaphila umbellata
    n 1: Eurasian herb with white or pinkish flowers in a terminal
         corymb [syn: love-in-winter, western prince's pine,
         Chimaphila umbellata, Chimaphila corymbosa]