pinafore

noun

1. a child’s apron, usually large enough to cover the dress and sometimes trimmed with flounces.
2. a woman’s sleeveless garment derived from it, low-necked, tying or buttoning in the back, and worn as an apron or as a dress, usually over a blouse, a sweater, or another dress.
3. Chiefly British.
   1. a large apron worn by adults.
   2. a sleeveless smock.

noun

1. mainly British an apron, esp one with a bib
2. mainly British short for pinafore dress
3. mainly US an overdress buttoning at the back

n.“sleeveless apron worn by children,” 1782, from pin (v.) + afore “on the front.” So called because it was originally pinned to a dress front.