Definition

A Southern regionalism for an alligator, particularly common in Cajun Louisiana where these prehistoric reptiles are as common as pickup trucks. If you see one while out on the bayou, you've probably already named it and accepted it as a neighbor.

Example Usage

Take the big pirogue, I saw a huge swamp dog sunbathing near the dock earlier.

Source: Urban Dictionary (https://www.urbandictionary.com/define.php?term=swamp%20dog&defid=1749538)