The Collaborative International Dictionary of English v.0.48:

Patchouli \Pa*tchou"li\, Patchouly \Pa*tchou"ly\, n. [CF. F.
   patchouli; prob. of East Indian origin.]
   1. (Bot.) A small shrubby mintlike plant (Pogostemon cablin
      syn. Pogostemon Patchouli) of the East Indies, yielding
      an essential oil from which a highly valued perfume is
      made.

   Syn: pachouli, Pogostemon cablin.
        [1913 Webster]

   2. The heavy perfume made from the patchouli plant.
      [1913 Webster]

   Patchouly camphor (Chem.), a substance homologous with and
      resembling borneol, found in patchouly oil.
      [1913 Webster]

WordNet (r) 3.0 (2006):

patchouli
    n 1: small East Indian shrubby mint; fragrant oil from its
         leaves is used in perfumes [syn: patchouli, patchouly,
         pachouli, Pogostemon cablin]
    2: a heavy perfume made from the patchouli plant [syn:
       patchouli, patchouly, pachouli]