Sealyham terrier (sē´lēhăm´), breed of short-legged terrier developed in Wales in the second half of the 19th cent. It stands about 10 in. (25 cm) high at the shoulder and weighs about 20 lb (9 kg). Its weather-resistant double coat consists of a dense, soft underlayer and a hard, wiry topcoat. It may be solid white or white with lemon or tan markings on the head and ears. The Sealyham takes its name from the Welsh country estate of Captain John Edwardes, who originated the breed. Used for years to hunt badger, otter, and fox, today it has come to be a popular house pet. See dog.