A Flailer is one of those mysterious friends that one day just disappearers off your Facebook friend list without any reason. If you have a large friend list, you may never figure out who it was and why they deleted, blocked or whatevered you. Not only is it rude ,but may cause negative feelings and nobody wants that.
You keep adding new friends but the number stated on your home page always stays the same... or goes down! You keep seeing your "good friend from high school" name in your suggested friend box, but you know you have added them already...three times! They are "Flailing" cause they are: Flailers"!
a flailer is that guy you might have seen like at the convenient store, he bounces when he walks, and kinda spins when he turns a corner, he over exaggerates his movements... like digging extra extra deep into his pocket while reaching for change... (you know you've seen the type, the fidgety meth-head) that dudes a flailer.