Frostbite is what happens when living flesh gets too cold for too long — usually fingers, toes, ears, or the nose. The part first goes numb and pale or grey; later it can swell, turn dark, and in the worst cases the tissue dies and may have to be taken off. People get it in hard winters, on high mountains, or at sea. It is a medical word, but ordinary people use it too. You also hear it as a verb, though ‘you’ll get frostbite’ or ‘your fingers will get frostbitten’ sounds more natural than ‘you’ll frostbite your fingers.’ Though actually, a bit of red, itchy swelling from damp cold is usually something milder (chilblains), not frostbite. Frostbite is the serious one.