(1) An increase of force or strength; denoting specifically the increased sharpness of the patellar reflex when the patient at the same time closes a fist tightly or pulls against flexed fingers or contracts some other set of muscles.Jendrassik maneuver. (2) In dentistry, a structural addition or inclusion used to give additional strength in function; e.g., bars in plastic denture base. (3) In conditioning, the totality of the process in which the conditioned stimulus is followed by presentation of the unconditioned stimulus, which itself elicits the response to be conditioned.reinforcer, schedules of reinforcement, under schedule, classical conditioning, operant conditioning.