Make sure to reference external image links from glossary images only.

or if you are using import/export to move the glossary to the same site and you have site admin or related manager permissions:

Instead of doing a XML file, go to the glossary inside the old course and then click on backup. The include enrolled users will be checked, leave it that way and and check Anonymize user data. Continue the backup then restore to the new course. Leave the settings on the restore alone. I was able to pull through the images whether they were attachments or were in the definition textbox. It did not really pull in the enrolled students. It also allowed students who were not in the previous course from which I made the back up view the pictures, but were in the new course to view the pictures/entries.

1. Create a new glossary in a course, insert files in description
2. Add an entry to this glossary that includes an image as part of the HTML definition, attach some files to the entry
3. Select 'Export entries' under Glossary administration in the settings block, go through the export process.
4. Create another glossary in a different course.
5. Select 'Import entries' under Glossary administration in the settings block, and import the file you created in step 3.
6. Verify that the imported entry still contains the embedded files and attachments
7. Import entries in a new glossary
8. Verify that intro has all embedded files and also files in the entry are also imported.