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.
This doesnt mean anything other than NEWPORT, RI.
These initials are what makes Newporters feel like they're reppin some type of hood. Hate it our love it, It's how we roll.