- (zoology) The periphery of a whorl extended to form a more or less flattened plate; a prominent spiral ridge.
- (nautical) Sometimes, a rigid, flat piece of material anchored to the lowest part of the hull of a ship to give it greater control and stability.
- A material similar to chalk or crayon used to mark pavement.
- A brewer's cooling vat.
- (nautical) A large beam along the underside of a ship’s hull from bow to stern.
- (nautical) A type of flat-bottomed boat.
- (botany) The two lowest petals of the corolla of a papilionaceous flower, united and enclosing the stamens and pistil; a carina.
- (aeronautics) In a dirigible, a construction similar in form and use to a ship's keel; in an aeroplane, a fin or fixed surface employed to increase stability and to hold the machine to its course.
- (intransitive, followed by "over") to collapse, to fall
"He keeled over after having a stroke."
- To turn up the keel; to show the bottom.
- To traverse with a keel; to navigate.