WordNet (r) 3.0 (2006):

cyberspace
    n 1: a computer network consisting of a worldwide network of
         computer networks that use the TCP/IP network protocols to
         facilitate data transmission and exchange [syn: internet,
         net, cyberspace]

The Jargon File (version 4.4.7, 29 Dec 2003):

cyberspace
 /si:'br?spays`/, n.

    1. Notional ?information-space? loaded with visual cues and navigable with
    brain-computer interfaces called cyberspace decks; a characteristic prop of
    cyberpunk SF. Serious efforts to construct virtual reality interfaces
    modeled explicitly on Gibsonian cyberspace are under way, using more
    conventional devices such as glove sensors and binocular TV headsets. Few
    hackers are prepared to deny outright the possibility of a cyberspace
    someday evolving out of the network (see the network).

    2. The Internet or Matrix (sense #2) as a whole, considered as a crude
    cyberspace (sense 1). Although this usage became widely popular in the
    mainstream press during 1994 when the Internet exploded into public
    awareness, it is strongly deprecated among hackers because the Internet
    does not meet the high, SF-inspired standards they have for true cyberspace
    technology. Thus, this use of the term usually tags a wannabee or
    outsider. Oppose meatspace.

    3. Occasionally, the metaphoric location of the mind of a person in hack
    mode. Some hackers report experiencing strong synesthetic imagery when in
    hack mode; interestingly, independent reports from multiple sources suggest
    that there are common features to the experience. In particular, the
    dominant colors of this subjective cyberspace are often gray and silver,
    and the imagery often involves constellations of marching dots, elaborate
    shifting patterns of lines and angles, or moire patterns.


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

cyberspace

    /si:'ber-spays/ 1. (Coined by William Gibson)
   Notional "information-space" loaded with visual cues and
   navigable with brain-computer interfaces called "cyberspace
   decks"; a characteristic prop of cyberpunk SF.  In 1991
   serious efforts to construct virtual reality interfaces
   modelled explicitly on Gibsonian cyberspace were already under
   way, using more conventional devices such as glove sensors and
   binocular TV headsets.  Few hackers are prepared to deny
   outright the possibility of a cyberspace someday evolving out
   of the network (see network, the).

   2. Occasionally, the metaphoric location of the mind of a
   person in hack mode.  Some hackers report experiencing
   strong eidetic imagery when in hack mode; interestingly,
   independent reports from multiple sources suggest that there
   are common features to the experience.  In particular, the
   dominant colours of this subjective "cyberspace" are often
   grey and silver, and the imagery often involves constellations
   of marching dots, elaborate shifting patterns of lines and
   angles, or moire patterns.

   [Jargon File]

   (1999-02-01)