keel 1 (k?l)n.1. Nautical a. The principal structural member of a boat or ship, running along the center of the hull from bow to stern, to which the ribs are attached.b. A projecting ridge or fin on the bottom of the hull of a boat or ship that improves directional control and is often weighted for added stability.2. The principal structural member of an aircraft, resembling a ship’s keel in shape and function.3. A structure, such as the breastbone of a bird, that resembles a ship’s keel in function or shape.4. A pair of united petals in certain flowers, as those of many members of the pea family.intr. & tr.v. keeled, keel·ing, keels Nautical To capsize or cause to capsize.Phrasal Verb: keel over To collapse or fall into or as if into a faint.[Middle English kele, from Old Norse kjölr.]keel 2 (k?l)n.1. Nautical a. A sail-powered barge, especially one historically used on the rivers of northern England.b. The load capacity of this barge.2. A British unit of weight formerly used for coal, equal to about 21.2 long tons.[Middle English kele, from Middle Dutch kiel.]keel 3 (k?l)tr.v. keeled, keel·ing, keels Chiefly British To make cool.[Middle English kelen, from Old English c?lan, to cool; see gel- in Indo-European roots.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.keel (ki?l) n1. (Nautical Terms) one of the main longitudinal structural members of a vessel to which the frames are fastened and that may extend into the water to provide lateral stability2. on an even keel well-balanced; steady3. (Aeronautics) any structure corresponding to or resembling the keel of a ship, such as the central member along the bottom of an aircraft fuselage4. (Biology) biology a ridgelike part; carina5. a poetic word for shipvbto capsize[C14: from Old Norse kjölr; related to Middle Dutch kiel, keel2] ?keel-less adjkeel (ki?l) n1. (Nautical Terms) a flat-bottomed vessel, esp one used for carrying coal2. (Units) a measure of coal equal to about 21 tons[C14 kele, from Middle Dutch kiel; compare Old English c?ol ship]keel (ki?l) nred ochre stain used for marking sheep, timber, etcvb (tr) to mark with this stain[Old English c?lan, from c?l cool]keel (ki?l) vb an archaic word for cool[C15: probably from Scottish Gaelic c?l]keel (ki?l) n (Veterinary Science) a fatal disease of young ducks, characterized by intestinal bleeding caused by Salmonella bacteria[C19: from keel1; see keel over]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014keel1 (kil) n. 1. a central fore-and-aft structural member in the bottom of a ship’s hull extending from the stem to the sternpost. 2. a ship; boat. 3. a part corresponding to a ship’s keel in some other structure, as in a dirigible balloon. 4. (cap.) the constellation Carina. 5. carina. v.t., v.i. 6. to turn or upset so as to bring the wrong side or part uppermost. 7. keel over, a. to capsize or overturn. b. to fall in or as if in a faint. Idioms: on an even keel, in a steady, stable, or calm state. [1325?75; Middle English kele