When does a tenant become a multi-tenant?

I am having trouble understanding the docs terminology on Multi Tenant.

Multi-tenant: Azure tenants that access other services in a shared environment, across multiple organizations, are considered multi-tenant.

I understand the concept of a Mult-tenant SaaS database as explained in the docs here which is similar to Wikipedia's explanation

But what is a multi-tenant tenant?

From the same terminology the definition of a tenant is

Azure tenant: A dedicated and trusted instance of Azure AD that's automatically created when your organization signs up for a Microsoft cloud service subscription, such as Microsoft Azure, Microsoft Intune, or Office 365. An Azure tenant represents a single organization.

So presumably a multi tenant tenant represents multiple organisations. I just don't see how.

It is a bit like calling a set a multi-set. A contradiction in terms.