Definitions for "Process identifier"
Keywords:  pid, kernel, unix, unique, fork
An integer used by the Unix kernel to uniquely identify a process. PIDs are returned by the fork system call and can be passed to wait() or kill() to perform actions on the given process.
Shown in the heading of the ps command as PID. The unique number assigned to every process running in the system.
(in UNIX) that is native to a machine or operating system.