$ sudo apt-get remove 9wm 

Uninstall 9wm including dependent package

If you would like to remove 9wm and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove 9wm 

Use Purging 9wm

If you use with purge options to 9wm package all the configuration and dependent packages will be removed.

$ sudo apt-get purge 9wm 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove 9wm 

See Also,