RDF

From Wiki Gonzalez

RDF = Really Damn Funny.

It was started in the Primer chat on IRC by GGT and supported by Dan Werr. Support in the Primer Lounge soon followed. It was created to counter LOL, which is so fucking annoying. Other variants proposed include CSL (Can't Stop Laughing) and LSHTMAFOOMA (Laughing So Hard That Monkeys Are Flying Out Of My Ass). These two haven't quite caught on...yet.