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[for a person] to fall over or fall down in a faint or in death. It was so hot in the room that two people just keeled over.
keel something over
Rur. to push something over. He leaned on the flimsy wall and keeled it right over. The high wind keeled over that sorry old fence.
1. to fall down suddenly because of illness or weakness Working outside in this heat, she was afraid someone would keel over.
2. (slang) to die suddenly The old man simply keeled over on the sidewalk from a heart attack, I suppose.
Etymology: based on the idea of a boat that keels over (turns over) with its keel (bottom) up
Collapse, as if in a faint; also, faint. For example, When she heard the awful news, she keeled over. This term alludes to a vessel rolling on its keel and capsizing. [Mid-1800s]
1. To fall over; capsize: The ship keeled over when it hit the iceberg.
2. To collapse or fall into or as if into a faint: I keeled over when I heard the bad news.