Phrase where you don't really care what happens, you're just glad it's not you who has to do the said person's task.
DUDE 1: My Mom wants me to go on a diet where I have to eat only lemons and cabbage and drink only prune juice.
DUDE 2: Good luck with that. (Thinking: Haha! Loser!)
by Jim E. Junk May 3, 2006
A sarcastic remark to a pointless endeavour.
"I want to move to Hollywood in attempt to marry a movie star!"

"Yeah? Good luck with that."
by Wize One July 13, 2008
This shows that courtesy is not dead. It's a very elegant urban code for, "I DONT CARE" but more accurately,"I REALLY DON'T GIVE A FLYING FUCK".
In some communities it means "YEAH, LIKE THAT'S GOING TO HAPPEN". So if something actually does happen you can never be called out and say it never happen.
expl.Friend 1. I would like to study computers. There is good money in it and you dont have to work so hard.

Friend 2.You aren't logic minded enough to study computers,"good luck with that"!
by Urban Dictionary November 11, 2006
Simple phrase used to catch out British spies or agents when masquerading as the enemy. When wished 'Good luck' in English by a foreign agent they find it literally impossible not to reply with 'Thanks old bean!' or something similar.

Most famously used in The Great Escape.
Hans Nazihausen: Halt! Sprechen sie Englisch?
John Smithson: Nein! Der English sind Schwein-poopen.
Hans: Haha, Ja. Good luck.
John: Thanks old bean!
Hans: AHA!
John: Oh bother.
by Horace Wimp January 13, 2008
a phrase used to wish someone well in an endeavor

sometimes a pointless phrase if the task at hand does not even remotely involve or require luck.
good luck washing those dishes. i hope the knives don't fall on your foot and slice your toes off!
by Insufficient Postage February 2, 2006
A sarcastic remark to a pointless endeavour.
"I want to move to Hollywood in attempt to marry a movie star!"

"Yeah? Good luck with that."
by Wize One July 13, 2008
"I'm trying to shoot at the Arclight"
"Haha, good luck..."
by ehannah October 24, 2008