Organizational Citizenship Behavior or OCB define as individual behavior that is discretionary, not directly or explicitly recognized by the formal reward system, and in the agregate promotes the efficient and effective functioning of the organization.
~Organ, Podsakoff, Mackenzie, 2006~
Discretionary means specific behavior in a specific context is not an absolute requirements of the job description (i.e., the literal or specificiable terms of the person's employment contract with the organization). Rather, the behavior involves some degree of personal choice, such that the person wil not be punished if he or she choose not to engage in the bahavior.
The last part of OCB requires that in the aggregate promotes the efficient and effective functioning of the organization. Most OCB actions, taken singly, would not make a dent in the overall performance of an organization; but summing across time for a single person and across persons in group will enhance effectiveness.
*By Prof. Dr. Wan Rafaei Abdul Rahman, Department of Psychology, IIUM. Keynote speaker for 5th seminar of psychology and human development, FSSK, UKM on 23 December 2008.