I've heard this idiom several times. But I can't find it in my dictionary.
Some forums in my country said it means "really" or it expresses surprise, and they give me an example:
-I make it!
-You don't say!
-Don't mock me! I‘ll beat him.
But it doesn't fit the context of the samples I've encountered.
For example:
A: Mr. Qian, what does he do exactly?
B: Gambling, man! What do you think?
A: Brother! You, me, and him, we're gonna work together.I tell you now. We're gonna work this out.
B: You don't say!
I feel it means "It's obvious. You don't need to tell me that."
Could someone be kind to tell me what exactly this idiom means?
Best Answer
It basically means exactly what you say that's super obvious or you don't need to even say that.
Another one people often use to say the same thing would be calling someone captain obvious.
A site to read for a good definition of this: You don't say in the The Free Dictionary
Look at the second definition: 2.Inf. You have just said something that everybody already knows.
The first definition you might here though is the non-sarcastic one, which is a genuinely surprised response to something someone said.