Keel
in botany, (1) the two lower petals of a papilionaceous corolla which adhere by their margins so as somewhat to resemble the keel of a boat; called also carina. (2) The midrib of a leaf or petal, etc., elevated externally. As a nautical term, a low, flat-bottomed vessel used in the river Tyne; a coal-barge. In shipbuilding, the lower longitudinal beam of a vessel, answering to the spine, and from which the ribs proceed. In wooden vessels an additional timber beneath is called the false keel. A sliding keel is a board amidships, working in a trunk in the line of the keel, and extending from the bottom to the deck. It is lowered to prevent a vessel's making leeway when sailing with side wind. In zoölogy, a projecting ridge along any surface; as, for instance, the back or horns of an animal. a