$ sudo apt-get remove octave-gsl 

Uninstall octave-gsl including dependent package

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

$ sudo apt-get remove --auto-remove octave-gsl 

Use Purging octave-gsl

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

$ sudo apt-get purge octave-gsl 

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 octave-gsl 

See Also,