When an application is unresponsive in CentOS it sometimes requires the task be terminated. This is a neat trick to closing a application with minimal command line use.

Start by opening your terminal. Then type the following command:

[sixthpoint@new-host ~]$ xkill

Now click on the window you want to terminate. The program will automatically get the pid from the application window and terminate the process.

Output after click:

xkill: killing creator of resource 0x4a00034