oh,ok, if you don't understant "XXX" you just say :"XXX 是什么意思？“ is OK!^_^

The most accurate way：。。。是什麼意思？which corresponds exactly to What does 。。。 mean。 。。。是什麼 is more equavalent to “What is 。。。” If you want to sound more conversational when speaking ，you can add an “啊”to the end of both sentences to make them sound more informal ，but better not to do it when writing 。 so 。。。是什麼意思啊？ or 。。。是什麼啊 ，both of which sound more informal and casual than they would without 啊at the end 。Hope this helps。