An Orphan process is a computer process whose parent process has finished or terminated, though it remains running itself. In Normally an orphan means someone whose parents are dead the same thing is followed here. A running process whose parents are dead, that means parents are either terminated, killed or exited but the child process is still alive.
In a Unix-like operating system any orphaned process will be immediately adopted by the special init system process: the kernel sets the parent to init. This operation is called re-parenting and occurs automatically. Even though technically the process has the “init” process as its parent, it is still called an orphan process since the process that originally created it no longer exists.
In other systems orphaned processes are immediately terminated by the kernel.
Killing a Orphan Process:
As orphaned processes waste server resources, so we need to kill those orphan processes.
To kill a orphan process is same as killing a normal process.
# kill -15 <PID>
If that don’t work then simply use
# kill -9 <PID>