Formal:
* Que voulez-vous dire? (This is the most literal and formal translation.)
* Que signifie cela? (This means "What does that mean?")
* Pouvez-vous préciser? (This means "Could you clarify?")
Informal:
* Tu veux dire quoi? (This is the most common informal translation.)
* Qu'est-ce que tu veux dire? (This means "What do you want to say?")
* C'est quoi, ça? (This means "What's that?")
Other options:
* Je ne comprends pas. (This means "I don't understand.")
* Expliquez-moi. (This means "Explain it to me.")
It's important to choose the translation that best fits the situation and the tone you want to convey.