Meaning/Usage: Used to tell someone that they will not get what they want.
Explanation: Many wishes do not come true. This expression is telling the person that what they want will be only a wish and not reality.
"You want straight A's like her? You wish!"
"You think she'll go on a date with you? You wish!"
"You think you're going to beat my high score? Don't you wish."
A. "I really need to win the lottery so I can retire."
B. "Ha! You wish!"
Other Common Sentences
"In your dreams."
"It's not going to happen."