standard time in the 8th time zone west of Greenwich, reckoned at the 120th meridian west; used in far western states of the United States
"The flight schedule listed a departure from Los Angeles at 6 PM PST."
Initialism of Pacific Standard Time.
"The meeting was scheduled to begin at 9 a.m. pst, so everyone adjusted their clocks accordingly."
In plain English: PST stands for Pacific Standard Time, which is used to describe how late it gets on the West Coast compared to other parts of the country.
"The teacher asked for a quiet moment to give us some pst before starting the exam."
Alternative form of psst
"Pst, don't tell anyone about our surprise party."