in Ancient Geography, two islands of this name in the sea lying between Britain and Ireland. The one described by Caesar, as situated in the middle passage between both islands, called Mona (Ptolemy); Mona, or Monobia (Pliny), is supposed to be the isle of Man.—Another Mona (Tacitus); an island more to the south, separated from the coast of the Ordovices by a narrow strait. The ancient seat of the Druids. Now called Anglesey, the island of the Angles or English.

an island of the Baltic sea, south-west of the island of Zealand, subject to Denmark. E. Long. 12° 30'. N. Lat. 55° 20'.