What term describes a process that has ended but has not been acknowledged by its parent process?

The term that describes a process that has ended but has not been acknowledged by its parent process is known as a "zombie" process. When a child process completes its execution, it sends an exit status to its parent process. Until the parent process reads this exit status using system calls like wait(), the child process remains in a zombie state. This is a necessary mechanism in UNIX-like operating systems, as it allows the parent to retrieve information about the child's termination while still preventing the system from prematurely removing it from the process table.

While the term "defunct" is also used interchangeably to describe zombie processes, the more commonly accepted term in the industry is "zombie." The other options like "ghost" and "foreign" do not refer to recognized states of processes within an operating system and are not relevant to the process states defined in UNIX/Linux systems.