Pronunciation: (shûrt),[key] —n. 1. a long- or short-sleeved garment for the upper part of the body, usually lightweight and having a collar and a front opening.
2. an undergarment of cotton, or other material, for the upper part of the body.
3. a shirtwaist.
4. a nightshirt.
5. 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. 6. 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. 7. lose one's shirt,Informal.to lose all that one possesses; suffer a severe financial reverse: He lost his shirt in the stock market.