Rolling On the Floor Shitting MySelf Laughing My Ass Off.
The newest term indicating to the person you are typing to that you are laughing. It is also a protest against other terms of the same nature (such as 'lol', 'lmao', 'pmsl', 'rofl', 'roflmao') which have now become so over-used that their meaning have been rendered negligible. 'Rofsmslmao' as a rule must only ever be used if you are actually laughing (and not just giggling but literally wetting yourself) therefore this indicates to the person that they really have said/shown you/done something funny. It must also be spelt correctly otherwise it can lead to great confusion - e.g: rolling my ass off shitting on myself the laughing floor.
John: "wtf you think you're doing saying 'rofsmslmao' dude? I didn't even say something funny. Asshole"
Frank: "Hey get this, I spiked Mr.Jones's coffee with ecstasy in Maths today, and he was totally trippin' out halfway through algebra!"
Frank: "wtf's 'rofsmslmao'?"
Kenobi: "It's my new word, it means rolling on the floor shitting myself laughing my ass off, it's so I don't have to say 'lol' all the time"
Kenobi: "Forget it"