‘To fall off in respect of vigour or activity’ (W.); to lose power or strength; to flag, wane; to break down; figurative of the heart. Of the eyes…

intransitive. To fall into a fainting-fit; to faint.

intransitive. Of a person, animal, or plant: to decline in health; to weaken, wither, or become faint; to exist in a state of weakness or illness…

intransitive. To become exhausted; to fail, tire, faint, swoon.

intransitive. Of a person or animal: to drop or fall gently down to the ground, a seat, etc., through weakness, exhaustion, or inability to stand…

To fall into a swoon. Also with away.

To sink, go down, descend. Now only poetic; of the sun, day, etc.: to decline, draw to a close.

To break down in regard to vital energy, from exhaustion or disease.

intransitive. To become feeble, collapse, give way, break down. Also transitive, to cause to collapse; to injure or disable. Often with up.

to flake (out): to faint, fall asleep (from exhaustion, drunkenness, etc.). So flaked (out) participial adjective, exhausted; unconscious, asleep…