How to kill a <defunct> process with parent 1

The only way you could remove the zombie/defunct process, would be to kill the parent. Since the parent is init (pid 1), that would also take down your system.

This pretty much leaves you with two options.

• Manually modify the process table, eg. create a dummy process, link the defunct process as a child of the dummy, then kill them off. Quite dangerous, and you may have to manually clean up other process resources such as semaphores and file handles.
• Reboot the system.

I'd go with the second.

Check if there was a kernel panic,

# dmesg |tail

Check if the process is in "D" Unkillable sleep, where it's in kernel mode for some syscall which has not returned yet (either kernel oops, or some other reason) http://www.nabble.com/What-causes-an-unkillable-process--td20645581.html

You could try restarting init:

 # telinit u

Otherwise, I wouldn't worry too much. It's not running and it's not taking any resources and it's just there so the kernel can remember it.