The Collaborative International Dictionary of English v.0.48:

Rhamnaceous \Rham*na"ceous\, a. (Bot.)
   Of or pertaining to a natural order of shrubs and trees
   (Rhamnaceae, or Rhamneae) of which the buckthorn
   (Rhamnus) is the type. It includes also the New Jersey tea,
   the supple-jack, and one of the plants called lotus
   (Zizyphus).
   [1913 Webster]