“WHAT DO YOU THINK?” and “WHAT DO YOU MEAN?” are not the same, folks. I hear them being misused regularly during group or class discussions.
Whether you are discussing the latest Big Brother episode or your company’s new advertising strategy, if you want to know your friend’s or colleague’s opinion, then ask, “What do you think?“
On the other hand, when I explain a grammar point or a new word in the classroom and a student doesn’t understand, it is only right that he/she raises their hand and asks, “What do you mean?“ It’s the same during discussions. If you are not clear about what your partner has just said, use “What do you mean?” for him/her to repeat or explain again.
There is another interesting use for “What do you mean?” That is when someone says something you disagree with. Ladies, imagine the situation. You spend a couple of hours making yourselves (more) beautiful because your partner/boyfriend/husband promised to take you out to dinner that evening. Then when he comes to pick you up he suggests you stay in, order a take-away pizza and watch the football on TV together. I think it’s only fair to say, and in an angry tone, “What do you mean we’re staying home tonight?”