When an event is so ridiculously funny that the level of its humor transcends the communicative abilities of the English language. When "funny," "haha," "roflcopter" and even "lollersk8r" do not suffice. Then, it is time for the hilarbear to roar.
ZOMG, did you see Max fall off the roller coaster and break every bone in his body? Total hilarbear.
people who use abbrevs say it as a combination of hilarious and coolbeans
Person 1: Yo, I was falling down a flight of stairs and there was a guy at the bottom and I reached out hoping he would catch me but instead he stepped back and I grabbed his junk instead!
Person 2: OMG, that's hilarbeans!! LOL!
Person 1: ...