$ sudo apt-get remove irb1.8

Uninstall irb1.8 including dependent package

If you would like to remove irb1.8 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove irb1.8

Use Purging irb1.8

If you use with purge options to irb1.8 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge irb1.8

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 irb1.8

See Also,