出处：按学科分类—语言、文字 中国对外翻译出版公司《汉英成语词典》第60页（205字）
用做窃贼的代称，有时也比喻脱离实际的人，例昨夜不慎未锁前门，使梁上君子乘机而入，幸亏损失不大。
Last night I was careless and did not lock the front door．A thief got in but fortunately not much was lost．