Definition of Self-organization:
Ability of a system to spontaneously arrange its components or elements in a purposeful (non-random) manner, under appropriate conditions but without the help of an external agency. It is as if the system knows how to do its own thing. Many natural systems such as cells, chemical compounds, galaxies, organisms and planets show this property. Animal and human communities too display self organization: in every group a member emerges as the leader (who establishes order and rules) and everybody else follows him or her, usually willingly.
Meaning of Self-organization & Self-organization Definition