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

push media

    A model of media distribution where items of
   content are sent to the user (viewer, listener, etc.) in a
   sequence, and at a rate, determined by a server to which the
   user has connected.  This contrasts with pull media where
   the user requests each item individually.  Push media usually
   entail some notion of a "channel" which the user selects and
   which delivers a particular kind of content.

   Broadcast television is (for the most part) the prototypical
   example of push media: you turn on the TV set, select a
   channel and shows and commercials stream out until you turn
   the set off.

   By contrast, the web is (mostly) the prototypical
   example of pull media: each "page", each bit of content, comes
   to the user only if he requests it; put down the keyboard and
   the mouse, and everything stops.

   At the time of writing (April 1997), much effort is being put
   into blurring the line between push media and pull media.
   Most of this is aimed at bringing more push media to the
   Internet, mainly as a way to disseminate advertising, since
   telling people about products they didn't know they wanted is
   very difficult in a strict pull media model.

   These emergent forms of push media are generally variations on
   targeted advertising mixed in with bits of useful content.
   "At home on your computer, the same system will run soothing
   screensavers underneath regular news flashes, all while
   keeping track, in one corner, of press releases from companies
   whose stocks you own.  With frequent commercial messages, of
   course."  (Wired, March 1997, page 12).

   Pointcast (http://pointcast.com) is probably the best
   known push system on the Internet at the time of writing.

   As part of the eternal desire to apply a fun new words to
   boring old things, "push" is occasionally used to mean nothing
   more than email spam.

   (1997-04-10)