To blow someone’s cover 意為「暴露某人的真實身份；揭穿某人的底細；暴露某人真正的目的或意圖；揭發某人隱藏的動機」。這個慣用語使用至今已有約 100 年之久，其中動詞 blow 意為「洩漏」(expose)，而這項用法可追溯到莎士比亞時期。
例句：
- The murderer fled the country shortly after he realized that someone had blown his cover. (那位殺人兇手在知道有人揭穿他的身份後不久就逃到了國外)
- Peter totally blew his own cover because he stupidly wore his school jacket to destroy the other team’s flag. (彼得完全暴露了他自己的身份，因為他愚蠢地穿著他的學校外套去破壞別隊的旗幟)