You can uninstall or removes an installed chromium-browser package itself from Ubuntu 14.04 LTS (Trusty Tahr) through the terminal,
$ sudo apt-get remove chromium-browser
If you would like to remove chromium-browser and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove chromium-browser
If you use with purge options to chromium-browser package all the configuration and dependent packages will be removed.
$ sudo apt-get purge chromium-browser
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 chromium-browser