The Collaborative International Dictionary of English v.0.48:

Harrisia \Harrisia\ prop. n. (Bot.)
   A genus of slender often treelike spiny cacti with solitary
   showy nocturnal white or pink flowers; Florida and Caribbean
   to South America.

   Syn: genus Harrisia.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Harrisia
    n 1: genus of slender often treelike spiny cacti with solitary
         showy nocturnal white or pink flowers; Florida and
         Caribbean to South America [syn: Harrisia, genus
         Harrisia]