Classic movie that came out in 1942, and probably has the best known lines in film history. For example:
"Here's looking at you, kid"
"If that plane leaves the ground and you're not with him, you'll regret it. Maybe not today, maybe not tomorrow, but soon — and for the rest of your life."
"Louis, I think this is the beginning of a beautiful friendship."
"We'll always have Paris."
Casablanca is a hella good movie. Too bad most people my age can't see that.
Moron:"OMFg its in balck and white so it must suck lol1100zzzone!!"
Me (or smart person): So?
An absolute classic.
Although that word is based on the movie 'Casablanca', it does not have to be a romantic movie from the 40's. It simply must be considered a 'classic' for its genre, even if it's something like fanfiction where nothing has been around for many years.
"After the End" by Arabella and Zsenya is considered the Casablanca of Harry Potter fanfiction.
"Hamlet" is the Casablanca of tragic theater.