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.

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.

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.

so your boat doesn't flip over, idiot

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.