if two people are at cross purposes, they do not understand each other because they are talking about or aiming at different things, without realizing it(由于谈论或针对不同事情而未意识到的)相互不理解,相互误解
I think we're talking at cross purposes; that's not what I meant at all.我想我们是说到两下里去了,我根本不是那个意思。