- Characterized by either a complete response or by a total lack of response or effect, as in neurological action above a threshold: "Nerve impulses follow the All or None Law—that is, a nerve impulse generated by a weak stimulus is just as strong as one generated by a strong stimulus” ( Fundamentals of Biology). (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.