1 An early coastal merchant ship. ‘The consensus is that the cog, which began as a small flat-bottomed coaster in the 10th century, or earlier, was developed by the Germans, perhaps out of the Rhine, and had become by 1400 a ship of 200 tons or more, 90 or more feet (27 metres) long and 30 or more feet (9 metres) in the beam … The cog was built either without a keel or with a simple keel-plank from which stem and stern posts, straight but angled, rose sharply and in a straight line, the ship having a high freeboard. The bottom-planking was laid flush or edge to edge, the steep sides being clinker-built from the turn of the bilge. A bowsprit, or spar, at the bow, appeared in the 13th century and a small square sail slung under it helped the vessel to move to windward. Superstructures or “castles” were added fore and aft for purposes of defence, and a topcastle added to the mast. At the stern a windlass was used to raise sail and haul the anchor. The cog of this ilk dominated the northern carrying trade, particularly from the Baltic, for about 150 years’ (R. Hope, A New History of British Shipping (1988), 40). The round ship of medieval times was virtually a cog. See also nef.
2 A type of small sailing craft used for local commerce on the rivers Humber and Ouse in north-east England.