If for some reason you don't want the system to add project's glossary to your terminology repository, you will need to delete the entries from the glossary before closing a project,
- From the Workplace pane select Projects - In progress
- Find a translation project and open it's glossary package
- Select all the terms in the glossary package by clicking on the top checkbox (see the screenshot).
- Click Delete in the ribbon menu
You will be asked to confirm to delete the selected terms.