pffft

   [IRC]  A  metamorphic  expletive which can be used to convey emotion,
   particularly  shock  or  surprise, disgust or anger. The amplitude of
   the  reaction  can  be  measured  by  counting  intermediary  fs. For
   example:

<jrandom> someone stole my hotdog
<fred> pffft

<frodo> Cthulhu stole my hotdog
<joe> pffffffffffffft!

[glossary]