From Longman Dictionary of Contemporary Englishpinaforepin‧a‧fore /ˈpɪnəfɔː $ -fɔːr/ noun [countable] 1 (also pinafore dress British English)DCC a dress that does not cover your arms and under which you wear a shirt or blouse SYN jumper American English2 DCC (also pinny British English informal) a loose piece of clothing that does not cover your arms, worn over your clothes to keep them clean → apron
Examples from the Corpus
pinafore• The girls are dressed alike, in dark blue uniforms with white collars and black pinafores.• The inmates wore a uniform of pale blue, the girls with white pinafores.Origin pinafore (1700-1800) pin + afore “in front” ( → AFOREMENTIONED) 