WordNet (r) 3.0 (2006):

coordinated universal time
    n 1: Greenwich Mean Time updated with leap seconds [syn:
         coordinated universal time, UTC]

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

Coordinated Universal Time
CUT
ITU-T X.680
leap second
UTC
World Time
Zulu time

    (UTC, World Time) The standard time common to
   every place in the world.  UTC is derived from International
   Atomic Time (TAI) by the addition of a whole number of "leap
   seconds" to synchronise it with Universal Time 1 (UT1), thus
   allowing for the eccentricity of the Earth's orbit, the
   rotational axis tilt (23.5 degrees), but still showing the
   Earth's irregular rotation, on which UT1 is based.

   Coordinated Universal Time is expressed using a 24-hour clock
   and uses the Gregorian calendar.  It is used in aeroplane
   and ship navigation, where it also sometimes known by the
   military name, "Zulu time".  "Zulu" in the phonetic alphabet
   stands for "Z" which stands for longitude zero.

   UTC was defined by the International Radio Consultative
   Committee (CCIR), a predecessor of the ITU-T.  CCIR
   Recommendation 460-4, or ITU-T Recommendation X.680 (7/94),
   contains the full definition.

   The language-independent international abbreviation, UTC, is
   neither English nor French.  It means both "Coordinated
   Universal Time" and "Temps Universel Coordonné".

   BIPM
   (http://www.bipm.org/enus/5_Scientific/c_time/time_1.html).

   The Royal Observatory Greenwich
   (http://rog.nmm.ac.uk/leaflets/time/time.html).

   History of UTC and GMT
   (http://ecco.bsee.swin.edu.au/chronos/GMT-explained.html).

   U.S. National Institute of Standards & Technology
   (http://its.bldrdoc.gov/fs-1037/dir-009/_1277.htm).

   UK National Physical Laboratory
   (http://npl.co.uk/npl/ctm/time_scales.html).

   US Naval Observatory
   (http://tycho.usno.navy.mil/systime.html).

   International Telecommunications Union
   (http://itu.int/radioclub/rr/arts02.htm).

   Earth's irregular rotation (/pub/misc/earth_rotation).

   (2001-08-30)