noun.
A venomous serpent of the southern United States, a species of moccasin or Trigonocephalus: so called from a white streak along the lips.
the GNU version of the Collaborative International Dictionary of English
noun.
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.