or cottonmouth Either of two species of pit viper that inhabits marshy lowlands of the southeastern U.S. and Mexico. The U.S. species (Agkistrodon piscivorus) is called a cottonmouth because it threatens with the mouth open, showing the white interior. It is up to 5 ft (1.5 m) long and is completely black or brown with darker crossbands. A dangerous snake with a potentially lethal bite, it tends to stand its ground or move slowly away when alarmed. It will eat almost any small animal, including turtles, fishes, and birds. See also copperhead
{i} type of poisonous semiaquatic snake that lives in swamps and is found in southern United States, cottonmouth, moccasin; snake that looks like a poisonous water moccasin but is harmless