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?"
having your heart ripped 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