Source : WordNet®

Greenwich Mean Time
     n : the local time at the 0 meridian passing through Greenwich,
         England; it is the same everywhere [syn: {Greenwich Time},
          {GMT}, {universal time}, {UT}, {UT1}]

Source : Free On-Line Dictionary of Computing

Greenwich Mean Time
     
         (GMT) The local time on the Greenwich
        meridian, based on the hypothetical mean sun (which averages
        out the effects of the Earth's elliptical orbit and its tilted
        axis).  GMT is the basis of the civil time for the UK.
     
        In 1925 the reference point was changed from noon to midnight
        and it was recommended that the term "{Universal Time}" should
        be used for the new GMT.
     
        Authorities disagreed on whether GMT equates with {UT0} or
        {UT1}, however the differences between the two are of the
        order of thousandths of a second.  GMT is no longer used for
        scientific purposes.
     
        (2001-08-02)