How do I uninstall Drush?
It seems there is no single remove command, so you need to:


Edit your composer.json file, e.g.

vim ~/.composer/composer.json


and remove line containing drush. Save the file.
Update Composer PHP packages by:

composer global update


It will remove a globally installed drush.


If you don't have composer command in your PATH, try php composer.phar instead.

See: How to remove a package from composer?.