I believe that it's a registered trademark of CompuGlobalHyperMegaNet Inc. (formerly InterSlice LLC). Buzzwords at their best.

A Hypermedia API is essentially what a by-the-book REST API is. Most "REST" APIs don't meet the hypermedia requirement outlined in the original dissertation. But because the term REST has been generalized beyond what it actually was defined as, some purists have taken to calling truly RESTful APIs "Hypermedia APIs"

Twilio is a good example. It boils down to delivering links with API results. So, given the root endpoint, a client can navigate/discover available actions for data retrieval/manipulation.

You could certainly argue that it is a "buzz word" or whatever, but there is a fundamental lack of buzz around the subject. REST is one of those terms that has been beat to death. Used/misused to describe so many things so as to be useless. Hypermedia adds a specificity to the equation that is useful, at least to me.

I like Fowler's description of the Richardson Maturity Model[1], which describes the "levels" of RESTfulness an API can have, with a full-on hypermedia API being the top level. Steve Klabnik's "Designing Hypermedia APIs"[2] is also shaping up to be a good resource, though it isn't free.

[1] http://martinfowler.com/articles/richardsonMaturityModel.htm...

[2] http://designinghypermediaapis.com/