This word has come up with the advent of Instant Messaging. Pssst is the sound people make when they disagree with something someone said, and want to express their disapproval with one easily said syllable. This is the text version of that sound and has become a very useful word among my friends. Example: Guy1: You know, the Detroit Lions aren' that bad. Me: Pssst.
PSSST
Meaning of PSSST in English
Slang English vocab. Английский сленговый словарь. 2012