GMT GMT noun [uncountable]
Greenwich Mean Time; the time as measured at Greenwich in London, used as an international standard for measuring time:
• The accident happened at 9.33 a.m. GMT on 14 May.
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GMT UK US /ˌdʒiːemˈtiː/ noun [U] MEASURES
► ABBREVIATION for Greenwich Mean Time: the time at Greenwich in London on which times around the world are based: »
They began moving toward their vehicles shortly after 2000 GMT.
Financial and business terms. 2012.