In terms of a boat or ship it means to roll so far on its side that it cannot recover and thus it turns upside down in the water (to capsize or turn turtle).
In general terms it means to collapse in a faint, to black out, to swoon.
The keel is the bottom of a boat. If you "keel over," then you are bottom-up, or you have fallen over. This usually means became unconscious, not just fallen down.
keel refers to as two parts of a ship
Sally was so shocked by what she saw, she was afraid she would keel over. The yacht had a keel weighted with a tonne of lead.
On a ship or boat, the keel is the main structure along the bottom on which the rest of the frame is built. It could also mean when a boat keels (capsizes) over. It could also be the ridge on the front of a birds' breastbone.
Verb: The giant wave forced the ship to keel over on its side into the ocean, and all the men fell overboard. Noun: There was a large hole in the keel of the boat, so the vessel pulled into port to have it repaired.
Keel away from
so your boat doesn't flip over, idiot
I believe the complete term is "keel over". This sometimes referred to as a knockdown. If the keel turns straight up out of the water, your boat has "turned turtle". If a large wave turns your boat over end-to-end, you have been "pitch-poled". These conditions are usually cause by rogue winds, rogue waves, or lack of attention to the sails and weather conditions. They do not necessarily mean that the boat will sink.Another take:"Keeling" is a malaprop -- it's not really a word. People often say "keeling" when they mean heeling. When a boat heels, it tilts laterally, with the wind.The term "keeling over" is something else: it refers to a position when the boat shows its keel; the bottom-most part of the boat, which means it's turned turtle or gone upside down. So "keel over" is a legitimate term; keeling is not.
Center Vertical Keel
In Latin, carina is a word for boat, or the keel of a boat.
The keel of the boat is made of lead and weighs 600 lbs. Even though customers can make me feel upset sometimes, I try to keep an even keel when dealing with them. That boat will not be able to sail in such shallow water because of its large keel. Sailboats with a mast of any appreciable size need a keel to remain stable. I am so tired, I feel like I could keel over at any moment.
Anna Keel has written: 'I personaggi di Anna Keel'