A band tied tightly around an injured arm or leg, above the wound, to squeeze the blood vessels shut and stop heavy bleeding. It can be a proper medical device with a strap and a rod you twist, or in an emergency a belt, a scarf, or a strip of cloth with a stick pushed through and turned. That twisting is the whole idea of the word. You meet it in first-aid courses, in war and accident reporting, and in hospital talk; a nurse also uses the word for the softer band tied on your upper arm to make a vein stand up before taking blood, which stops nothing and only holds the blood back a moment. English says it roughly "TOOR-ni-kay" in British English and often "TUR-ni-kit" in American English — both are normal. People also use it as a picture in writing: a tourniquet on spending, meaning something clamped hard to stop a loss.