"What does Х mean?" = "'Х деген не?"
Yes, that's correct. There are other variants of how the same thing can be asked. "X деген нені білдіреді?"(it's the closest equivalent to "What does Х mean") "Х дегеніміз не?"(What is X?) Also, if you're asking for the meaning of a single word you can use this structure: X деген сөздің мағынасы қандай? (what is the meaning of the word X) The easiest one is of course Х деген не?
Hope that it'll help.