Inflected forms: re·in·forced, re·in·forc·ing, re·in·forc·es 1. To give more force or effectiveness to; strengthen: The news reinforced her hopes.2. To strengthen (a military force) with additional personnel or equipment. 3. To strengthen by adding extra support or material. 4. To increase the number or amount of; augment. 5.Psychologya. To reward (an experimental subject, for example) with a reinforcer subsequent to a desired response or performance. b. To encourage (a response) by means of a reinforcer.