In British English, contemporary outfit including a black jumper or pinafore dress. The term jumper describes what is called a sweater in American Jumper clothing british. In more formal British usage, a distinction is made between a pinafore dress and a pinafore. Though a related garment, in American English, has an open back and is worn as an apron.
Pinafore always refers to an apron. The apron dress may be viewed as a special case of the jumper. A Jumper may have a bodice with a completely closed back, wikimedia Commons has media related to Jumper dresses.