A Tennessee Rat Tail is when a man or woman takes a shit and takes the fecal matter and rolls it into a long stringy turd, and freezes it for strength. The shitter will then take their creation and insert it into their partners rectum, vagina, mouth, etc.
Dad: That's a nice Play-Doh Tennessee Rat Tail you made there. Your mother loves those.
Son: But it's a snake
Dad:Of course it is Richie...of course it is...