What does PSST stand for?

What does PSST mean?

PSST	Pressure Sore Status Tool Medical » Physiology
PSST	Professionally Speaking Singles Toastmasters Miscellaneous » Toastmasters
PSST	Photonics Simulation Software For Teaching Computing » Software
PSST	Plato Support Services Tip Computing » Software
PSST	Philippino Students Stand Together Academic & Science » Universities
PSST	Python Snippet Support Team Business » Firms
PSST	Periodic Significant Scheduled Tasks Governmental » NASA

psst(interj.): (used to attract someone's attention in an unobtrusive manner.)