English▸ noun the longitudinal structure along the centerline at the bottom of a vessel's hull, on which the rest of the hull is built, in some vessels extended downward as a blade or ridge to increase stability.
▪ Zoology a ridge along the breastbone of many birds to which the flight muscles are attached; the carina.
▪ Botany a prow-shaped pair of petals present in flowers of the pea family.
▪ literary a ship.
▸ verb [no object] (keel over) (of a boat or ship) turn over on its side; capsize:
it's going to take more wind to make this boat keel over.
▪ informal (of a person or thing) fall over; collapse:
a wardrobe was about to keel over on top of him.
– ORIGIN Middle English : from Old Norse kjǫlr, of Germanic origin.