look up any word, like ratchet:
 
1.
Really?
- Hey, did you hear? Jack got aids!
- You don't say?
by IchigoFB October 13, 2009
 
2.
No Shit
"Your going to have a baby??" "You dont say."
by jjhasmadskills December 21, 2008
 
3.
literally speaking it is just another way of saying a very commonly and aptly used phrase "NO SHIT". it is when stating the blatant obvious and saying it as if it was just thought of on the spot. It is used to show distaste in a rather sarcastic and underhanded way and if said properly can be funny to no ends.

a master of this would be Christoffer!!
person 1- sir i dont think the bomb exploded
Person 2- what gave that away, the lack of noise? or the lack of mushroom? or the lack of the afterwave?
person3- it was the no mushroom for me.
person4- you don't say!!!

at an airport gate waiting to be let into the flight
Person 1- so dude we are going on gate number 15 rite?
person 2- oh yeah so lets join the queue for gate 15.
after reaching the near end of the line
person 3- i think we have reached our gate
person 1 and 2- You don't say!!
by ronnie1234 November 05, 2010
 
4.
An expression which appears in rage comics as a cartoonized version of Nicolas Cage. The phrase is a response to anything obvious and functions the same as "No shit, Sherlock" and "thank you captain obvious".
Some guy: I'll tell you a big fact.
Me: And... what is it?
That very guy: Stars don't blink! It's the atmosphere that makes stars look like if they blink!
Me: You don't say?
by Definitiosis January 06, 2013
 
5.
Used to express sarcasm when someone states the obvious, or states a fact that has been delivered like a second ago
Fat man:Dude, I think I have become fat
Dude:You don't say
by cagedidiot July 25, 2013