/ˈswetˌSHərt/ noun. A loose, heavy shirt, typically made of cotton, worn when exercising or as leisurewear. Sweatshirts are arguably a type of sweater, but made of a fabric and cut similar to sweatpants. It is fashioned out of a thick, usually cotton jersey material. Sweatshirts are also almost exclusively casual attire and not dressy as some other sweaters may be.