Any California male who smokes weed and eats fast food, which normally ends up on a clean shirt. The person then becomes The Dirty Shirt, and will deny he is dirty regardless of how much crap he has on himself. To prove his point he will continue to wear the soiled shirt for days on end.
I saw Kurt in the garage smoking with Matt, and yes, Kurt is The Dirty Shirt tonight.
On Fridays you wear a shirt which you bought at a thrift store like Value Village and wear it every Friday without washing it until it is unwearable in which case you buy another.
Justin: That shirt looks terrible it must be Dirt Shirt Friday.