Similar to swamp donk
; but a legitimate term on its own and one that is easier to say.
Refers to a female or male (though the term is typically applied to chicks) who at one time might have been 'clean' (i.e., a dog) but that has now become dirty, annoying and untouchable (because it plays in swamps).
My neighbour Lauren is a swamp dog. She puked on my floor and plugged up my toilet too.