The term organization can have a very broad definition in reality. It can refer to both the ability to keep some sort of order to a number of things for the purposes of maintaining some level of logical grouping (such as keeping a group of items “organized”). It can also refer to a specific entity that is comprised of a group of individuals united in either cause or employment capacity. In terms of a strict project management definition, the term organization (which in some instances may be abbreviated for purposes of brevity through use of the three letter abbreviation “org”) is used for the purposes of referring to the sum total of the individuals who have been brought together under one umbrella, organized for a particular and specific purpose of performing or conducting a specific and unique type of work within a single enterprise. This enterprise can refer to a corporation, a non-profit group, or and other type of pre-existing group, and can also refer to a group of individuals who have been assembled for the sole purpose of accomplishing a specific one time task, such as the entire project team.
This term is defined in the 3rd edition of the PMBOK but not in the 4th.