Only the owner of the organization can delete it. If you are the owner of your organization and you delete it, you will also permanently delete all the projects and resources that belong to your organization, and there is no way that you or even the IT folks at BigML can retrieve them.
To delete an organization, please go to your organization account and click the Delete organization button.
A modal window will display asking for confirmation. You will need to insert the password of your personal account and click the Delete button.