The Collaborative International Dictionary of English v.0.48:

Peppermint \Pep"per*mint\, n. [Pepper + mint.]
   1. (Bot.) An aromatic and pungent plant of the genus Mentha
      (Mentha piperita), much used in medicine and
      confectionery.
      [1913 Webster]

   2. A volatile oil (oil of peppermint) distilled from the
      fresh herb; also, a well-known essence or spirit (essence
      of peppermint) obtained from it.
      [1913 Webster]

   3. A lozenge of sugar flavored with peppermint.
      [1913 Webster]

   Peppermint camphor. (Chem.) Same as Menthol.

   Peppermint tree (Bot.), a name given to several Australian
      species of gum tree (Eucalyptus amygdalina, Eucalyptus
      piperita, E. odorata, etc.) which have hard and durable
      wood, and yield an essential oil.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mint \Mint\ (m[i^]nt), n. [AS. minte, fr. L. mentha, Gr. mi`nqa,
   mi`nqh.] (Bot.)
   The name of several aromatic labiate plants, mostly of the
   genus Mentha, yielding odoriferous essential oils by
   distillation. See Mentha.
   [1913 Webster]

   Note:

   Corn mint is Mentha arvensis.

   Horsemint is Mentha sylvestris, and in the United States
      Monarda punctata, which differs from the true mints in
      several respects.

   Mountain mint is any species of the related genus
      Pycnanthemum, common in North America.

   Peppermint is Mentha piperita.

   Spearmint is Mentha viridis.

   Water mint is Mentha aquatica.
      [1913 Webster]

   Mint camphor. (Chem.) See Menthol.

   Mint julep. See Julep.

   Mint sauce, a sauce flavored with spearmint, for meats.
      [1913 Webster]

WordNet (r) 3.0 (2006):

peppermint
    n 1: herb with downy leaves and small purple or white flowers
         that yields a pungent oil used as a flavoring [syn:
         peppermint, Mentha piperita]
    2: red gum tree of Tasmania [syn: red gum, peppermint,
       peppermint gum, Eucalyptus amygdalina]
    3: a candy flavored with peppermint oil [syn: peppermint,
       peppermint candy]