The DICT Development Group

  moccasin \moc"ca*sin\, n. [An Indian word. Algonquin makisin.]
     [Sometimes written moccason.]
     1. A shoe made of deerskin, or other soft leather, the sole
        and upper part being one piece. It is the customary shoe
        worn by the American Indians.
        [1913 Webster]
  
     2. (Zool.) A poisonous snake of the Southern United States.
        The water moccasin ({Ancistrodon piscivorus syn.
        Agkistrodon piscivorus, also called cottonmouth and
        cottonmouth water moccasin) is usually found in or near
        water. Above, it is olive brown, barred with black;
        beneath, it is brownish yellow, mottled with darker. The
        upland moccasin is Ancistrodon atrofuscus. They resemble
        rattlesnakes, but are without rattles.
        [1913 Webster]
  
     Moccasin flower (Bot.), a species of lady's slipper
        ({Cypripedium acaule) found in North America. The lower
        petal is two inches long, and forms a rose-colored
        moccasin-shaped pouch. It grows in rich woods under
        coniferous trees.
        [1913 Webster]

  cottonmouth \cottonmouth\ n.
     venomous semiaquatic snake ({Agkistrodon piscivorus) of
     swamps in southern U.S.; -- called also water moccasin,
     cottonmouth moccasin, and cottonmouth water moccasin. It
     grows to a length of about 4 feet. The name refers to the
     whiteness of the lips and inside of the mouth.
  
     Syn: water moccasin, cottonmouth moccasin, Agkistrodon
          piscivorus.
          [WordNet 1.5 +PJC]