An individual that spends more time at their town's square than they do at their own home or at places of greater entertainment value. Often, a square rat will shout insults or jabs at passers by to reinforce their own self esteem. A square rat is not a good person.
Person A: "Man, the other the day, that kid who hangs out at the square all day started calling me a fag!"
Person B: "Yeah, he's just a square rat. Don't worry about him"