A cottonmouth is a venomous snake found in the swamps, lakes, and slow-moving streams of the southeastern United States. It gets its name from the white inside of its mouth, which it displays as a warning when threatened, making it look like it has a mouth full of cotton.

The cottonmouth is also called a water moccasin, and it's one of the few venomous snakes in North America that spends much of its time in or near water. Unlike most water snakes, which flee when approached, a cottonmouth often holds its ground and opens its mouth wide in that distinctive threat display. The snake's body is thick and dark, usually brown or black, helping it blend in with muddy riverbanks and cypress roots.

Cottonmouth can also describe the feeling of having a dry mouth, which can happen when you're sick, dehydrated, or in very cold weather.