I'm hysterical! in netspeak, 4 letters
OMG, that's hilarious, 4 letters
That's hilarious, in Internet-speak, 4 letters
That's too funny, to surfers, 4 letters
Guffaw in an AOL chat room, 4 letters
It's somewhat stronger than LOL, 4 letters
Netizen's That's hysterical!, 4 letters