Deleting the glossary and its components currently is a permanent delete-as in the attached screenshot/warning that a user gets when attempting a delete. Atlan creates a backup everyday and the best way to handle this would be to restore the backup snapshot from the previous day. Please note that this will override any other changes that were done in the instance in the present day.
There isn’t a direct way to cherry-pick and restore only specific things that have been deleted. We'd advise caution before doing any delete actions.