Uninstall mate-desktop

To remove just mate-desktop package itself from Debian execute on terminal:

sudo apt-get remove mate-desktop

Uninstall mate-desktop and it's dependent packages

To remove the mate-desktop package and any other dependant package which are no longer needed from Debian Jessie.

sudo apt-get remove –auto-remove mate-desktop

Purging mate-desktop

If you also want to delete configuration and/or data files of mate-desktop from Debian Jessie then this will work:

sudo apt-get purge mate-desktop

To delete configuration and/or data files of mate-desktop and it's dependencies from Debian Jessie then execute:

sudo apt-get purge –auto-remove mate-desktop