Free association refers to the principle technique in Freudian psychoanalysis in which patients give a running account of thoughts, feelings, mental images, and physical sensations as they occur, in order to derive a repressed or hidden motivation for their psychological disorder.
It is a Psychotherapeutic technique in which clients spontaneously express their thoughts and feelings exactly as they occur, with as little censorship as possible; a cardinal rule of Psychoanalysis in which patients are required to say anything and everything that comes to mind. Over time, free association is believed to shed light on unconscious thoughts and urges; method used in psychoanalysis in which the client speaks freely, saying whatever comes to mind. It is Freud's major tool for studying the contents of the unconscious mind. With free association, a patient is encouraged to express freely everything that comes to his or her mind; patient relates feelings, fantasies, thoughts, memories, and recent events to the analyst spontaneously and without censoring them. These associations give the analyst clues to the unconscious processes of the patient.
Other /More definition:
free association refers to Psychoanalytic therapy technique intended to explore threatening material repressed into the unconscious. The patient is instructed to say whatever comes to mind without censoring.