A polite way of writing, "Fuck knows." Also used to bypass content filters, parents, and illiterate jackasses.
Can also be used as an insult.
<kurobeastix>: how'd class go?
<shadowsong>: phuk nose. i didn't go.
<kurobeastix>: LAWL
<imanoob>: wanna cyba?
<shadowsong>: bug off, phuk nose.
<imanoob>: wat.