Locu, an arm of the sea, on the W. coast of Scotland, stretching into N. Argyllshire, and separating the district of Lorn from those of Morven and Sunart. It is 22 miles long from the southern extremity of Lismore Island to the mouth of Loch Eil, by 4 in average, and 12 in extreme breadth, at its entrance. It sends off four branch lochs,—viz., Lochs Etive, Creran, Leven, and Eil; and contains several islands, the chief of which are,—Lismore, Shuna, and Balnagowan. It communicates with the Caledonian Canal through Loch Eil. The scenery of its coasts is highly picturesque.