P911 Meaning in Chat or Text Messages Online

P911 is an internet slang used to indicate that a parent is nearby or listening in on a conversation. The "P" stands for "parent" and "911" is a reference to the emergency phone number used in the United States. This slang is often used by teenagers or young adults trying to communicate with their peers without being overheard by their parents.

Example:
Person 1: "Hey, did you finish that party invitation yet?"
Person 2: "Yeah, but shh, P911."
Person 1: "Okay, got it. We'll talk later."