$ sudo apt-get remove emacs23 

Uninstall emacs23 including dependent package

If you would like to remove emacs23 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove emacs23 

Use Purging emacs23

If you use with purge options to emacs23 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge emacs23 

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 emacs23 

See Also,