WordNet (r) 3.0 (2006):

hypermedia
    n 1: a multimedia system in which related items of information
         are connected and can be presented together [syn:
         hypermedia, hypermedia system, interactive
         multimedia, interactive multimedia system]

The Free On-line Dictionary of Computing (30 December 2018):

hypertext
hypermedia

    A term coined by Ted Nelson around 1965 for a
   collection of documents (or "nodes") containing
   cross-references or "links" which, with the aid of an
   interactive browser program, allow the reader to move easily
   from one document to another.

   The extension of hypertext to include other media - sound,
   graphics, and video - has been termed "hypermedia", but
   is usually just called "hypertext", especially since the
   advent of the web and HTML.

   (2000-09-10)