If a meeting is not relevant to you anymore, you can remove the meeting series. Removing a meeting series archives the meeting and moves it under 'Show removed meetings'. All meeting data is preserved and the meeting can be restored if needed. To remove the meeting series, click on the 'Edit' button of your meeting, scroll down and click on the 'Remove meeting series' button.
You can also delete a specific meeting instance if one instance is not relevant to a meeting series. For example, you have a recurring meeting on a specific day every week. One week you decide not to meet, because it's a public holiday or skip it for other reasons. You can open the relevant meeting, make sure it is not the 'Latest instance' (but an instance that already happened), and click on the three dots (...) > Delete' to delete the meeting instance.
Please note: If the existing meeting instance you have selected is the latest meeting instance (indicated by being the highest option in the drop-down), you will not be able to delete it. In this case, you will have to wait until the meeting has passed and delete it after.