The Collaborative International Dictionary
keel over \keel` o"ver\, v. i. To drop down in a faint, or as if dead; to die. [Colloq.]
Wiktionary
vb. 1 (context intransitive nautical English) Of a vessel: to roll so far on its side that it cannot recover; to capsize or turn turtle. 2 (context intransitive idiomatic English) To collapse in a faint; to black out; to die.
WordNet
v. turn over and fall; "the man had a heart attck and keeled over"
Usage examples of "keel over".
If anyone were to keel over with the first bite you can imagine Branson's reaction.
It was an odd, uncanny sound, like the scraping of a ship's keel over a submerged rock or coral reef.
Once every day or so someone would keel over, swaying or staggering or just falling limp as a sack of rice.
There he sat while a low rolling scraping sound shifted around him, disorienting him, and he fought to stay sitting and not simply keel over.
He stroked her hair, patted her back, and wondered whether she would just keel over on the floor if he jumped up to get her a glass of water.