Usually used as a quick Lay, When everyone else your haveing sex with is unavaliable.. A Last Resort.
EX: Man, That bitch is straight from the swamps. She let me hit that shit in the backseat for $5.. Such A swamp rat.
2)Usually people who are low lives. They don't have money.
Yeah i know i don't like them but they keep talking to me.
"you must have never seen a swamp rat before, that's nothing more than a yearling"
"Shit, that's some fucked up shit."