Noun - a fart. Taken from foul British sleave mag Viz, usually appearing in a speech bubble emanating from a cartoon character's nether regions. Used generally by teenage boys in onomatopoeic fashion, similar to the "scwhing" popularised by the movie Bill and Ted's Excellent Adventure.
Farp (in a quiet lift)
Farp (when asked by headmaster "what are you going to do with your life, boy")
Farp (during any publicly mandated moment of silence)
Phil: yo could you knock next time, you almost walked in on me farping.
Mario: oh that's what that smell was.
Phil: Ya I was farping up a storm in there.