This is a
sound, usually used in disgust, agrivation or disbelief. It can
mean a number of things, "such as screw you", "
whatever", "fuck off", or "yeah right"
MARY; OMG! I just got tickets to the concert
BARBIE: OMG! when are we going?
MARY: Well I can only bring one other
person, so I picked
Suzie
BABIE: PSSHHHT, I didnt even wanna go to that concert anyway.