a seaport borough in the hundred of Twrcelyn, in the island of Anglesey, North Wales. It has a harbour cut out of the rock with great labour and cost, capable of containing 30 vessels of about 200 tons burden. It rose rapidly after the discovery of the copper mines of Pary's Mountain, but since the ore there has been exhausted it has declined. It is 261 miles from London, and 15 from Beauvais. Population in 1851, 3169.