If you raise your arms and your shirt comes up above your belt.
If you're gonna wear that, keep your arms down, that looks like a jimmy shirt
When a man ejaculates, most often from jerkin his gherkin, and he shoots some man muck, most often by accident, onto his shirt.
Bill Clinton was renowned for walking the halls of the oral office with a little collateral shirt squirt on his outfit.
If it's under 65 degrees, it's sweat shirt weather and shirts are prohibited/ not suggested
"It's 63 degrees! Finally I don't have to wear a shirt."
"I love No Shirt Season!"
The person(s) you see during the day that have the same shirt on as you.
"Man, I saw seven shirt twins today!"
or when you see a shirt twin: "Dude! shirt twins! high five!"
A shirt a boy wears to look "cool" like Maddy B or Travis Tritch, but honey we all know your not in fact your the opposite sis. and thats the tea
Eww why is he wearing that hes having a nip slip. No no no its a nip shirt he must be a dweeb
A shirt worn to give the appearance of being older than the wearer actually is. Often used to purchase alcohol, or get into clubs, etc.
Tom: Hey Mike can you get us some beer for the party?
Mike: Sure just let me go get my errand shirt.
The mark that is left behind when you get sunburned with a T-shirt or tank top on.
Chad: Woah dude you've got a serious skin shirt. Want some 'screen?
Tanner: UV rays are just a conspiracy bro! I'll just take off my shirt and even it out.