A "t-shirt" is a type of casual and comfortable shirt that has short sleeves and a round neckline. It is often made of soft fabric and is commonly worn by people of all ages for everyday activities. Full definition
Note: the following restaurants are optional and formal dress is required: long trousers and T shirts with sleeves for gentlemen. (southwestvacations.com)
I've been living in T shirt dresses and maxi dressed this summer. (divinelifestyle.com)