cross-purposes
n(idm 习语) at cross-purposes (of people or groups) misunderstanding what the other side is talking about or concerned with (指人或团体)相互误解
We´re at cross-purposes
I´m talking about astronomy, you´re talking about astrology. 我们彼此误解了
我谈的是天文学, 你谈的是占星术.