Abbreviation “GMT” means “Got Me Tight.” A person might use this if they’re trying to express some degree of frustration with you. Usually over text message, Slack, Snapchat, or other online communication tools. It’s used to kind of say, “I’m feeling super tense right now about this conversation.”
This abbreviation is consideredsafe for children to use. And is considered work appropriate, but due to its informal language you may want to consider whether you use it or not.