A Zombie Process, in computing, is a process that has completed its execution but still has an entry in the process table. This is to allow the process that started the (now zombie) process to read its exit status.
The term 'zombie' is used because such a process is not working (it's 'dead'), but it's still present in the system. Zombies take up system resources, and if a system generates zombies faster than they can be reaped by their parents, the system will eventually run out of process slots or memory.
However, in most cases, zombie processes are harmless and can be safely ignored. They typically disappear from the process table as soon as their parent process reads the exit status.