The Collaborative International Dictionary of English v.0.48:

Global Positioning System \Glob"al Po*si"tion*ing Sys"tem\ n.
   (gl[=o]"b'l p[-o]*z[i^]sh"[u^]n*[i^]ng s[i^]s"t[e^]m)
   A worldwide system of electronic navigation in which a
   vessel, aircraft or missile determines its latitude and
   longitude by measuring the transmission time from several
   orbiting satellites. GPS is more precise than any other
   navigation system available, yielding position accurate
   within 10 meters 95% of the time.

   Syn: GPS.
        [RDH]

   Note: The precision of the GPS is dependent upon the very
         high timing accuracy of atomic clocks. Although the
         military originally intentionally degraded the signal
         and thus the accuracy for civilian users, GPS was
         nevertheless more precise than any other navigation
         system available. In 2000, President Clinton issued an
         executive order discontinuing the degrading of the
         signal for civilians.
         [RDH]

               On June 26, 1993 . . . the U.S. Air Force
               launched the 24th Navstar satellite into orbit,
               completing a network of 24 satellites known as
               the Global Positioning System, or GPS. With a GPS
               receiver that costs less than a few hundred
               dollars you can instantly learn your location on
               the planet -- your latitude, longitude, and even
               altitude -- to within a few hundred feet.
               This incredible new technology was made possible
               by a combination of scientific and engineering
               advances, particularly development of the world's
               most accurate timepieces: atomic clocks that are
               precise to within a billionth of a second.

                                                  --http://www4.nationalacademies.org/beyond/beyonddiscovery.nsf/web/gps?OpenDocument
         [PJC]

WordNet (r) 3.0 (2006):

Global Positioning System
    n 1: a navigational system involving satellites and computers
         that can determine the latitude and longitude of a receiver
         on Earth by computing the time difference for signals from
         different satellites to reach the receiver [syn: Global
         Positioning System, GPS]

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

Global Positioning System
GPS

    (GPS) A system for determining postion on the
   Earth's surface by comparing radio signals from several
   satellites.  When completed the system will consist of 24
   satellites equipped with radio transmitters and atomic clocks.

   Depending on your geographic location, the GPS receiver
   samples data from up to six satellites, it then calculates the
   time taken for each satellite signal to reach the GPS
   receiver, and from the difference in time of reception,
   determines your location.

   ["Global Positioning by Satellite"?  Precison?  Coverage?  Web
   page?]

   (1998-02-10)