[1] : The Collaborative International Dictionary of English v.0.48

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
see also:
agkistrodon piscivorus water moccasin cottonmouth moccasin cottonmouth water moccasin agkistrodon piscivorus 

[2] : WordNet (r) 2.0

cottonmouth moccasin
     n : venomous semiaquatic snake of swamps in southern united
         states syn: water moccasin, cottonmouth, agkistrodon
         piscivorus
see also:
water moccasin cottonmouth agkistrodon piscivorus 

Cottonmouth >> C Words
Cottonmouth, definition of term: Cottonmouth
cottonmouth_pag1.html

Moccasin >> M Words
Moccasin, definition of term: Moccasin
moccasin_pag1.html

Water Moccasin >> W Words
Water Moccasin, definition of term: Water Moccasin
water+moccasin_pag1.html