The Collaborative International Dictionary of English v.0.48:

Roselle \Ro*selle"\, n. (Bot.)
   a malvaceous plant (Hibiscus Sabdariffa) cultivated in the
   east and West Indies for its fleshy calyxes, which are used
   for making tarts and jelly and an acid drink.
   [1913 Webster]

WordNet (r) 3.0 (2006):

roselle
    n 1: East Indian sparsely prickly annual herb or perennial
         subshrub widely cultivated for its fleshy calyxes used in
         tarts and jelly and for its bast fiber [syn: roselle,
         rozelle, sorrel, red sorrel, Jamaica sorrel,
         Hibiscus sabdariffa]