A person who is so stupid they dont deserve being called a reatard once but twice in the same word. This can also be used when the words fucktard, dumbass, and moron just cant portray and person's lack of simple intellegence.
This applies to people who are constantly late. Generally people in their teen years as they have not completely come to appreciate punctualality as a sign of adulthood.
"Hey! We will never make it to anything on time if you don't stop acting like a bunch of Tardy Tards!"