user@machine:~$ ps -U user | grep defunct
19547 ? 00:00:00 gnome-pty-helpe <defunct>
26875 ? 00:00:00 netstat <defunct>
user@machine:~$ kill -9 19547;kill -9 26875
user@machine:~$ ps -U user | grep defunct
19547 ? 00:00:00 gnome-pty-helpe <defunct>
26875 ? 00:00:00 netstat <defunct>
ender@machine:~$ sudo su
Password:
root@machine:/home/user # cd
root@machine:~ # ps -U user | grep defunct
19547 ? 00:00:00 gnome-pty-helpe <defunct>
26875 ? 00:00:00 netstat <defunct>
root@machine:~ # kill -9 19547;kill -9 26875
root@machine:~ # ps -U user | grep defunct
19547 ? 00:00:00 gnome-pty-helpe <defunct>
26875 ? 00:00:00 netstat <defunct>

So, how in the hell do I kill these processes?

My screensaver locked my computer up hard, couldn't get it to jump to alt-F1 or anything else, but machine was still up. Managed to ssh in via another machine (ubuntu as well, but no graphics as ubuntu doesn't like to recognize this monitor under default settings), there was one zombie process according to top, killed out the xscreensaver and a few other things, no more zombie in top. But screensaver image is still locked unto the machine.

Then tried killing Mozilla, no luck.

Tried killing nautilus and a buncha gnome things, and clock and whatever else wouldn't take down my stuff. No luck.

A little later one of those things musta eventually come down and brought down the screensaver as well. ps -U showed most of the processes back up, under new PIDs, but no idea which one was the one to take it down.

I'm now up to two defunct processes which I can't seem to get rid of...

Of course, a hard reboot will do it. As will an axe.
You could soft reboot or restart gnome or restart X?

killall xscreensaver ... did you try that?

$ ps -U simon | grep defunct
22853 ? 00:00:00 netstat <defunct>
15699 ? 00:00:00 gnome-pty-helpe <defunct>

I got this by:

$ killall gnome-pty-helpe
gnome-pty-helpe: no process killed

but a subsequent check turned up both the above defunct.
repeated attempts to kill the process gives no output and the entries remain.

Just so you know this behavior is not just you