The act of fainting, syncope.
"The sudden noise caused him to have a faint and collapse on the floor."
In plain English: A faint is an old-fashioned word for being very weak, sickly, or lacking strength.
"The faint smell of perfume drifted through the room."
To lose consciousness through a lack of oxygen or nutrients to the brain, usually as a result of suddenly reduced blood flow (may be caused by emotional trauma, loss of blood or various medical conditions).
"When she stood up too quickly from a hot shower, she felt dizzy and immediately fainted."
In plain English: To faint means to lose consciousness and fall down because you feel very weak or dizzy.
"The room became so stuffy that she began to faint from lack of fresh air."
weak and likely to lose consciousness
"suddenly felt faint from the pain"
"was sick and faint from hunger"
"felt light in the head"
"a swooning fit"
"light-headed with wine"
"light-headed from lack of sleep"
indistinctly understood or felt or perceived
"a faint clue to the origin of the mystery"
"haven't the faintest idea"
lacking conviction or boldness or courage
"faint heart ne'er won fair lady"
Lacking strength; weak; languid; inclined to lose consciousness
"The soldier felt faint from exhaustion and nearly collapsed in the heat of battle."
In plain English: Faint means barely visible, audible, or noticeable because it is very weak or distant.
"The old house looked faint and gray in the twilight."
Usage: Use "faint" only when describing something that is visibly pale or lacking color and vitality; avoid it for general weakness where "feeble" or "frail" might be more precise. Do not use the adjective to describe a person who has simply lost consciousness, as that state requires the verb form.
The word "faint" comes from the Old French verb meaning to shape or form in thought, which originally referred to pretending or imagining something rather than a physical sensation of weakness. It traveled into Middle English as faynt with this sense of being feigned before evolving to describe someone who is weak or nearly unconscious.