[ree-in-fawrs, -fohrs]
verb (used with object), re·in·forced, re·in·forc·ing.
  1. to strengthen with some added piece, support, or material: to reinforce a wall.
  2. to strengthen (a military force) with additional personnel, ships, or aircraft: to reinforce a garrison.
  3. to strengthen; make more forcible or effective: to reinforce efforts.
  4. to augment; increase: to reinforce a supply.
  5. Psychology. to strengthen the probability of (a response to a given stimulus) by giving or withholding a reward.
  1. something that reinforces.
  2. a metal band on the rear part of the bore of a gun, where the explosion occurs.
Also reenforce, re-enforce.

Origin of reinforce

1590–1600; re- + inforce, alteration of enforce
Related formsre·in·forc·er, nounself-re·in·forc·ing, adjectiveun·re·in·forced, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for reinforcer


verb (tr)
  1. to give added strength or support to
  2. to give added emphasis to; stress, support, or increasehis rudeness reinforced my determination
  3. to give added support to (a military force) by providing more men, supplies, etc
  4. psychol to reward an action or response of (a human or animal) so that it becomes more likely to occur again
Derived Formsreinforcement, noun

Word Origin for reinforce

C17: from obsolete renforce, from French renforcer; see re- + inforce enforce
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for reinforcer



c.1600, originally in military sense, from re- "again" + enforce (cf. re-enforce). Related: Reinforced; reinforcing.

Online Etymology Dictionary, © 2010 Douglas Harper

reinforcer in Medicine


  1. A stimulus, such as a reward, that in operant conditioning maintains or strengthens a desired response.


  1. To give more force or effectiveness to something; strengthen.
  2. To reward an individual, especially an experimental subject, with a reinforcer subsequent to a desired response or performance.
  3. To stimulate a response by means of a reinforcer.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.