Jac shirt

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A heavy shirt, which is often worn in place of a jacket during the Fall or the Spring seasons. The name originates from "jacket" and "shirt". A jac shirt may have buttons or a zippered front. A jac shirt usually has two breast pockets and may have front hand pockets as well. Jac shirts are usually worn indoors and outdoors alike.