consciousness
He lost consciousness after his accident and never regained it.
She never lost consciousness throughout the whole gruelling experience.
Above that altitude, people can function for only a few minutes without oxygen before becoming groggy and losing consciousness.
He felt himself losing consciousness and then someone slapping him round the face.

SMART Vocabulary: related words and phrases

Losing consciousness
black
catatonia
concuss
concussed
concussion
go out like a lightidiom
hypnotic
hypnotically
in a drunken stupor
insensibility
knock
light
pass
pass out
senseless
stun
swoon
unconsciousness
unresponsive
unresponsiveness