"GTT" most commonly refers to a Glucose Tolerance Test, a medical exam for diagnosing diabetes by measuring how your body processes sugar, but it can also stand for companies like GTT Communications (a global tech/network provider) or historical phrases like Gone to Texas. To know what "GTT" means, you need context, but in health, it's about blood sugar; in business, it's likely about networks or data; historically, it's about migration.