The "raspberry" sound that you make with your mouth. There's really no way to spell it so this is how its symbolized.

Ex) From Family guy:

STEWIE: PASS THE MASHED POTATOES MEG
PETER: ~~~
STEWIE: MEG
PETER: ~~~
MEG: WHY ARE YOU MAKING THAT NOISE AFTER SOMEONE SAYS MY NAME?
LUIS: STOP BEING RUDE TO MEG.
PETER: ~~~~~~~~~
by hjdubz February 3, 2009
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