T-shirt

T-shirt BrE AmE, tee-shirt /ˈtiː ʃɜːt $ -ʃɜːrt/ noun [countable]
[Date: 1900-2000; Origin: Because it is shaped like the letter T]
a soft shirt with short ↑sleeves and no collar:
She was wearing jeans and a T-shirt.

Oxford Advanced Learner's Dictionary

T-shirt

ˈT-shirt [T-shirt T-shirts] (also ˈtee shirt) noun

an informal shirt with short sleeves and no collar or buttons, or just a few buttons at the top
See also: tee shirt
Example Bank:

• He was wearing a faded pair of blue jeans and a ratty old T-shirt.

Cambridge Advanced Learner's Dictionary

Cambridge Advanced Learner's Dictionary - 4th Edition

ˈ T-shirt / ˈtiː.ʃɜːt / / -ʃɝːt / noun [ C ] ( also ˈ tee shirt )

A1 a simple piece of clothing, usually with short sleeves and no collar, that covers the top part of the body:

She was wearing jeans and a T-shirt.

Collins COBUILD Advanced Learner’s English Dictionary

T-shirt

also tee-shirt
(T-shirts)

A T-shirt is a cotton shirt with no collar or buttons. T-shirts usually have short sleeves.

N-COUNT

Merriam-Webster's Advanced Learner's Dictionary

Merriam-Webster's Advanced Learner's Dictionary:

T-shirt

T–shirt also tee shirt /ˈtiːˌʃɚt/ noun, pl T–shirts also tee shirts [count] : a shirt that has short sleeves and no collar and that is usually made of cotton

noun