What does keel mean?
A keel is the long structural ridge forming the backbone of a ship or boat, running along its underside. The term can also refer to the lower edge of a vessel, the vessel as a whole, or a similar ridge on the body of an animal. Nautical expressions such as "lay the keel" describe beginning the construction of a ship, while "on an even keel" means stable, balanced, or proceeding smoothly. The verb "keel" is chiefly encountered in "keel over," meaning to overturn or become destabilized. Although the word is strongly associated with ships, it is not limited to maritime language: zoological and anatomical contexts use it for animal structures that resemble a vessel's keel. Its long history and the survival of the phrase "on an even keel" make it useful both for precise description and vivid figurative expression.
The long structural beam or ridge running along the bottom of a ship or boat; also, by extension, the vessel itself or a comparable ridge on an animal's body.
"Inspectors checked the keel of the vessel before approving it for service."
The nautical sense is standard in British and American English. Animal and anatomical uses are relatively specialized.
To capsize or overturn, especially as a result of wind or loss of balance; figuratively, to become or cause to become destabilized.
"The powerful gust nearly keeled the boat over."
Usually used in the phrase "keel over."
The plural is used when referring to the keels of multiple vessels or to separate structural components.
"The harbour's old wooden keels were preserved as historical artefacts."
A ship's keel is its backbone: damage or instability there can affect the entire vessel.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of keel
The word comes from Old English cēol, meaning the bottom or keel of a ship. It was borrowed from Old Norse kjǫlr, a cognate still reflected in Scandinavian forms such as Swedish köl. Related forms survive in Dutch kiel and German Kiel, all referring to a ship's keel or the vessel's principal structural line.
Related word forms
How keel is actually used
In its structural sense, keel is chiefly nautical. The expression "on an even keel" is common in general English for a stable, balanced condition. As a verb, "keel over" can mean either to capsize or, figuratively, to collapse or become destabilized.