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 favour of John de Ligne, lord of Barbazon, who took the name of Arenberg. It is seated on the river Aer. Long. 6° 44' E. Lat. 50° 27' N.