POSSE is an acronym/abbreviation for Publish (on your) Own Site, Syndicate Elsewhere. It’s a Syndication Model where the flow involves posting your content on your own domain first, then syndicating out copies to 3rd party services with perma(short)links back to the original version.
via IndieWebCamp.
Looks interesting with respect to my quest to self-host what I post to social media. Thanks to @lewiscowper for bringing it to my attention.