a small town of Germany, in the circle of Westphalia, defended by a castle. It is the capital of a county of the same name, and was erected into a principality by the emperor Maximilian II. in favor of John de Ligne, lord of Barbazon, who took the name of Arenberg. It is seated on the river Aer, E. Long. 7. 3. N. Lat. 50. 27.