$ sudo apt-get remove libgd-ruby 

Uninstall libgd-ruby including dependent package

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

$ sudo apt-get remove --auto-remove libgd-ruby 

Use Purging libgd-ruby

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

$ sudo apt-get purge libgd-ruby 

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 libgd-ruby 

See Also,