Meaning of all-or-none law

all'-or-none' law"

Pronunciation: (ôl'ur-nun'), [key]
— Physiol. Physiol.
  1. the principle that under given conditions the response of a nerve or muscle fiber to a stimulus at any strength above the threshold is the same: the muscle or nerve responds completely or not at all.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.