T-shirt

[tee-shurt] /ˈtiˌʃɜrt/
noun
1.
a lightweight, usually knitted, pullover shirt, close-fitting and with a round neckline and short sleeves, worn as an undershirt or outer garment.
Also, tee-shirt.
Also called T, tee.
Origin
1940-45; named from its shape
British Dictionary definitions for T-shirt

T-shirt

noun
1.
a lightweight simple garment for the upper body, usually short-sleeved
Word Origin
so called because of its shape
Word Origin and History for T-shirt
n.

1920, in reference to the shape it makes when laid out flat.