The Collaborative International Dictionary of English v.0.48:

Phlorizin \Phlor"i*zin\, n. [Gr. ?, ?, bark + "ri`za root.]
   (Chem.)
   A bitter white crystalline glucoside extracted from the root
   bark of the apple, pear, cherry, plum, etc. [Formerly also
   written phloridzin.]
   [1913 Webster]