"Mastodon" is too specific and "Fediverse" too technical. How about "Social Web?" As in:

* I have a Social Web account.
* I saw it on the Social Web
* Let's see what the Social Web thinks!
* Publish it on the Social Web.
* He's been on the Social Web all day.
* I'm building a new Social Web service.
* The Social Web is federated.
* Mastodon is a Social Web service and application.
* What's the Social Web's future?
* ActivityPub is a Social Web protocol.
* Will the #SocialWeb end civilization?