An acrimonious quarrel or argument between two people that usually results in estrangement. The two people in question must always be extremely close; i.e best friends or family members. It can also be more than two, although that doesn't happen very often.
There are two possible outcomes of a falling-out:
-The friends will no longer be on speaking terms for awhile, but eventually reconcile.
Or...
-The friends will no longer be on speaking terms. Period.
"Did you hear Alan and Blake are no longer friends?"
"What? I thought they were inseparable!"
"Not really...they had a falling out after finding out that Alan's girlfriend was cheating on him with Blake."
having your heartripped out because you love someone but you don't see a future with them and you can't really break up with them because you don't have a legitimate reason for breaking up with the other person beside you don't feel like being with them anymore.
person 1: dude what's wrong?
person 2: I'm falling out of love with my girl
person 1: that sucks
person 2 : It does, because I don't know what to do about it