From Longman Dictionary of Contemporary Englishgmgm (plural gm or gms)TMthe written abbreviation of gram or gramsGMGM /ˌdʒiː ˈem/ adjective British English (genetically modified) GM foods or plants have had their genetic structure changed so that they are not affected by particular diseases or harmful insectsFrom Longman Business Dictionarygmgm written abbreviation for GRAM; GROSS MARGINGMGM abbreviation for GENETICALLY MODIFIED; GENETIC MODIFICATION
