A sarcastic way of responding to - or interrupting – someone who is busy telling you about their master plan and all the unrealistically fantastic things they think will happen to them. By using this expression you are suggesting the only place their desired outcome is likely to happen is in their dreams.
Daniels: One day I’ll be mayor of this city!
Smith: In your dreams! Who would vote for you?
(idiomatic expression) To express denial, to refuse a proposal. Same as "I don't even think about it" or "Fuck you, I won't do it!".
"Drop your weapon!"
"In your dreams..." (during a robbery)
used to refer to something that is desired by the speaker or the person spoken to but is unlikely to happen
I would make you an awesome video game in your dreams.
What you think and what she feels are two different things.
You may be handsome and charming, but she is NOT your 'ex'... because that would mean (at one time) you were worthy and A gentleMAN... in your dreams!
Instead, you are a... a... a word that has yet to be invented. And a big one at that!
P.S., the only way she would lay naked with you, is in a mass grave! :D