a long- or short-sleeved garment for the upper part of the body, usually lightweight and having a collar and a front opening.

an undergarment of cotton, or other material, for the upper part of the body.

a shirtwaist.

a nightshirt. ?

in one's shirt sleeves

without a coat

It was so hot that they worked in their shirt sleeves. Also, in one's shirt-sleeves.

keep one's shirt on

Informal . to refrain from becoming angry or impatient; remain calm

Tell him to keep his shirt on until we're ready.

lose one's shirt

Informal . to lose all that one possesses; suffer a severe financial reverse

He lost his shirt in the stock market.

noun

blouse , camise , chemise , dress , jersey , polo , pullover , sark , shift , silk , smock , sport , tunic , turtleneck