無言以對(duì) not find one’s tongue
起初他還挺硬，可是當(dāng)警察出示經(jīng)他篡改的文件并問他是怎么一回事的時(shí)候，他卻無言以對(duì)了。
He was arrogant at the beginning, but the moment when the police showed the documents he had doctored and asked him what the matter was, he could not find his tongue.