SRS BSNS
A contraction of 'Serious Business', popularly used among the Red vs Blue forums, as well as various other ports of call around the internet.
It's main use is mocking, when someone takes the internet too seriously or takes a joke too seriously, people will often remark on how it is "srs bsns".
Teh internets is srs bsns
I was mocking the Audi calling it a sedan basically.