(1) one or more organizations sharing a definite mission, goals, and objectives to offer an output such as a product or service. (ISO 15704 2000)
(2) An organization (or cross organizational entity) supporting a defined business scope and mission that includes interdependent resources (people, organizations and technologies) that must coordinate their functions and share information in support of a common mission (or set of related missions). (CIO Council 1999)
(3) the term enterprise can be defined in one of two ways. The first is when the entity being considered is tightly bounded and directed by a single executive function. The second is when organizational boundaries are less well defined and where there may be multiple owners in terms of direction of the resources being employed. The common factor is that both entities exist to achieve specified outcomes. (MOD 2004)
(4) A complex, (adaptive) socio-technical system that comprises interdependent resources of people, processes, information, and technology that must interact with each other and their environment in support of a common mission. (Giachetti 2010)
(1) ISO 15704. 2000. Industrial Automation Systems -- Requirements for Enterprise-Reference Architectures and Methodologies. Geneva, Switzerland: International Organization for Standardization (ISO), ISO 15704:2000.
(2) CIO Council. 1999. Federal Enterprise Architecture Framework (FEAF). Washington, DC, USA: Chief Information Officer (CIO) Council.
(3) MOD. 2004. Ministry of Defence Architecture Framework (MODAF), version 2. London, UK: U.K. Ministry of Defence.
(4) Giachetti, R. E. 2010. "Design of Enterprise Systems: Theory, Architecture, and Methods." Boca Raton, FL, USA: CRC Press, Taylor and Francis Group.
Definition (1) above is the SEBoK preferred definition. The focus of this definition is on purpose rather than structure, and the enterprise may be either enduring or transient, and either formally or informally constituted and governed. The simplest case of enterprise could be an individual and the largest a national or international undertaking.
Definition (2) is compatible with definition (1) and provides additional insight relevant to the practice of "enterprise architecting", which is closely related to Enterprise Systems Engineering.
Definition (3) highlights the fact that the word "enterprise" is sometimes used synonymously with "business". However in the SEBoK the term business is used to refer to a form of organization, while an enterprise often involves collaboration across organizational boundaries. Furthermore, we also use prodcut and team to refer to two other forms of an organization. An enterprise could be at the business level, but some enterprises are at the project or team level. Therefore, as noted above, it is better to focus on the purpose rather than structure of an "enterprise" to facilitate the more proper use and better understanding of that term.
Definition (4) highlights the socio-technical nature of the enterprise and its ability to be adaptable to changing circumstances.