How to force quit or stop a program

After running a job, only to find out later that it is stuck at some point and even Control-C cannot stop it.

e.g. a infinite loop script, X program that stuck in the X window & etc.

1. Find out the program ID by running :

ps aux | grep -i <program glob>

where <program glob> is part of the name of the program to terminate.
e.g.

ps aux | grep -i thunderbird

2. The second column with digits will be the program ID.

3. Force terminate it by :

kill -9

Voilla !!!