ermine, name for a number of northern species of weasel having white coats in winter, and highly prized for their white fur. It most commonly refers to the white phase of Mustela erminea, called short-tailed weasel in North America and stoat in the Old World. The white pelts are made into wraps, coats, and trimmings. The black-tipped tails are used in the United States as ornament, and in Europe they were used with the ermine of royal robes.