How to uninstall crossfire-client-x11 from Ubuntu
To uninstall just crossfire-client-x11 package itself from Ubuntu execute on terminal:
sudo apt-get remove crossfire-client-x11
Uninstall crossfire-client-x11 and it's dependent packages
To uninstall the crossfire-client-x11 package and any other dependant package which are no longer needed on Ubuntu.
sudo apt-get autoremove crossfire-client-x11
If you also want to delete configuration and/or data files of crossfire-client-x11 from Ubuntu then this will work:
sudo apt-get purge crossfire-client-x11
To delete configuration and/or data files of crossfire-client-x11 and it's dependencies from Ubuntu then execute:
sudo apt-get autoremove --purge crossfire-client-x11
crossfire-client-x11 package information
XLib Client of the game Crossfire
Crossfire is "a multiplayer graphical arcade and adventure game made for the X environment. It has certain flavours from other games, especially Gauntlet (TM) and Nethack/Moria. Any number of players can move around in their own window, finding and using items and battle monsters. They can choose to cooperate or compete in the same 'world'." To play the game you'll need to have access to a local or remote server.
More information about apt-get remove
Advanced Package Tool, or APT, is a free software user interface that works with core libraries to handle the installation and removal of software on Debian, Ubuntu and other Linux distributions. APT simplifies the process of managing software on Unix-like computer systems by automating the retrieval, configuration and installation of software packages, either from precompiled files or by compiling source code.
apt-get is the command-line tool for handling packages, and may be considered the user's "back-end" to other tools using the APT library.
apt-get remove is identical to install except that packages are removed instead of installed. Note that removing a package leaves its configuration files on the system. If a plus sign is appended to the package name (with no intervening space), the identified package will be installed instead of removed.