​NEAGH (nā′äh), LOUGH, the largest lake of the British Islands, in the province of Ulster, Ireland, surrounded by the counties of Armagh, Tyrone, Londonderry, Antrim, and Down; length 16 miles; average breadth, 10 miles. It receives the waters of numerous streams, of which the principal are the Upper Bann, the Blackwater, and the Callan; and its surplus waters are carried off N. to the North Channel by the Lower Bann. Communication by means of canals subsists between the Lough and Belfast, Newry, and the Tyrone coalfield.