vest/vɛst; vest/n [C] 1 BrE a piece of underwear that you wear under a shirt [ undershirt AmE 【美】]【英】〔上身〕内衣﹐汗衫2 a special piece of clothing without SLEEVES that you wear to protect your body 防护背心: a bulletproof vest 一件防弹背心3 AmE a piece of clothing without SLEEVES and with buttons down the front that you wear as part of a suit [ waistcoat BrE 【英】]【美】马甲﹐西装背心