dirt rat Share definition Flag Someone who is just plain dirty, looks like they haven't showered in a month, and when you looks at them you get a chill down your spine. The biggest dirt rats have big teeth. Eww, teresa looks so ugly, shes such a dirt rat. dirt rat by Eric E. July 26, 2006 0 0 Get merch Get the dirt rat mug. Buy Now — $32.95 See more merch