butter wouldn't melt in someone's mouth idiom
装老实相
used when someone looks as if they would never do anything wrong, although you feel they might
Tommy looked as if butter wouldn't melt in his mouth. 汤米装出一副老实相。
英汉双解词典收录81607条英汉双解翻译词条，基本涵盖了全部常用单词的读音、翻译及用法，是英语学习的有利工具。