Daily Chinese Idiom Guessing Game
To not think it is so; to disagree with or not approve of something.
然是，对。不认为是对的。表示不同意或否定。
宋·苏轼《再乞罢详定役法状》右臣先曾奏论前衙一役，只当招募，不当定差，执政不以为然。”
When she suggested changing the plan, he shook his head, implying that he thought otherwise.