As an administrator user of an organization, you have the option to define who are the user roles with permissions to modify a TX glossary of a specific project in Transifex
In order to do that:
Visit your organization settings page and click on Glossary
Click on the gear icon of the specific glossary you want to define the permissions for and then click 'User Permissions'
In the pop-up window, define who are the user roles you want to have the permissions to add/edit/delete glossary entries
Once you apply the changes, the user roles who haven't been checked will no longer be authorized to apply changes to your project's glossary. A proper message will appear to them in Transifex Web Editor: