From German - English Ding/FreeDict dictionary ver. 1.9-fd1:
Pst! /pˌeːˌɛstˈeː/ <int>
Hush! Shush! <int>, Ssh! <int>, Shh! <int>, Whist! <int> [Sc.] [Ir.] , Whisht! <int> [Sc.] [Ir.] , Wheesht! <int> [Sc.] [Ir.] , Hist! <int> [archaic]
Note: used to call for silence
"Pst! Willst du das ganze Haus aufwecken?" - Hush! Do you want to wake everyone?
Synonyms: Psst!, Pscht!, Sch!
see: pst! sagen