To change so as to match or fit; cause to correspond. To bring into proper relationship. To adapt or conform, as to new conditions: "unable to adjust themselves to their environment\u201d ( Karl A. Menninger). See Synonyms at adapt. To bring the components of into a more effective or efficient calibration or state: adjust the timing of a car's engine. In chiropracty, to manipulate (the spine and other body structures) to treat disorders and restore normal function of the nervous system. To decide how much is to be paid on (an insurance claim). To adapt oneself; conform. To achieve a psychological balance with regard to one's external environment, one's needs, and the demands of others.