Habafa- a word of excitement, horror, confusion, or any exclamation really.
Used when they can't think of a way to express the feeling they're experiencing, or they just want to use somethingunique. It is more often used online, as it's quite difficult to pronounce habafa.
Person 1: "DUDE DOJA CATJUST COMMENTED ON YOUR POST AND SAID THAT THEY LOVE YOUR WORK"
This term is sometimes used to denote that a user is present but essentially AFK (away from keyboard). This usually applies when somebody is playing a game, watching a movie, or doing something else that prevents them from being able to receive and reply to some form of messages within a reasonable period of time.
IRC:
User: Hey guys, I'll have to catch you later.
<<User changes his/her nickname to User|HBAFK.>>
IM:
User: I'm going to go hbafk while I play some Day of Defeat.
OtherDude: Ok, see ya.