See information system.
Sources:
FIPS 200 under SYSTEM
NIST SP 800-128 under System
NIST SP 800-137 under System
NIST SP 800-172
NIST SP 800-18 Rev. 1 under System
NIST SP 800-30 Rev. 1 under System
NIST SP 800-39 under System
NIST SP 800-60 Vol. 1 Rev. 1 under System
NIST SP 800-60 Vol. 2 Rev. 1 under System
NIST SP 800-171 Rev. 2

  A discrete set of resources organized for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information.
Sources:
NIST SP 800-34 Rev. 1 under Information System from 44 U.S.C., Sec. 3502

  The term 'information system' means a discrete set of information resources organized for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information.
Sources:
NIST SP 800-59 under Information System from 44 U.S.C., Sec. 3502 (8)

  Any organized assembly of resources and procedures united and regulated by interaction or interdependence to accomplish a set of specific functions. Note: Systems also include specialized systems such as industrial/process controls systems, telephone switching and private branch exchange (PBX) systems, and environmental control systems.
Sources:
NIST SP 800-12 Rev. 1 under System
NIST SP 800-128 from CNSSI 4009-2015

  Combination of interacting elements organized to achieve one or more stated purposes. Note 1: There are many types of systems. Examples include: general and special-purpose information systems; command, control, and communication systems; crypto modules; central process unit and graphics processor boards; industrial/process control systems; flight control systems; weapons, targeting, and fire control systems; medical devices and treatment systems; financial, banking, and merchandising transaction systems; and social networking systems. Note 2: The interacting elements in the definition of system include hardware, software, data, humans, processes, facilites, materials, and naturally occurring physical entities. Note 3: Systems of systems is included in the definition of system.
Sources:
NIST SP 800-37 Rev. 2 from ISO/IEC 15288

  Combination of interacting elements organized to achieve one or more stated purposes.
Sources:
NIST SP 800-160 Vol. 2 Rev. 1 from ISO/IEC/IEEE 15288:2015
NIST SP 800-161r1 from NIST SP 800-53 Rev. 5 - adapted
NIST SP 800-53A Rev. 5 from ISO/IEC/IEEE 15288:2015
NISTIR 8062 under System from ISO/IEC 15288

  Any organized assembly of resources and procedures united and regulated by interaction or interdependence to accomplish a set of specific functions. See information system (IS).
Sources:
CNSSI 4009-2015

  a collection of computing and/or communications components and otherresources that support one or more functional objectives of an organization. IT system resources include any IT component plus associated manual procedures and physical facilities that are used in the acquisition, storage, manipulation, display, and/or movement of data or to direct or monitor operating procedures. An IT system may consist of one or more computers and their related resources of any size. The resources that comprise a system do not have to be physically connected.
Sources:
NIST SP 800-16 under IT System

  A computer-based system used by an issuer to perform the functions necessary for PIV Card or Derived PIV Credential issuance as per [FIPS 201-2].
Sources:
NIST SP 800-79-2 under Information System

  Any organized assembly of resources and procedures united and regulated by interaction or interdependence to accomplish a set of specific functions. See information system. Note: Systems also include specialized systems such as industrial/process controls systems, telephone switching and private branch exchange (PBX) systems, and environmental control systems.
Sources:
NIST SP 800-37 Rev. 2 from CNSSI 4009-2015

  A discrete set of information resources organized for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information.
Sources:
NIST SP 1800-10B under Information System from FIPS 200, 44 U.S.C., Sec. 3502
NIST SP 1800-25B under Information System from FIPS 200, 44 U.S.C., Sec. 3502
NIST SP 1800-26B under Information System from FIPS 200, 44 U.S.C., Sec. 3502
NIST SP 800-128 under information system from 44 U.S.C., Sec. 3502
NIST SP 800-137 under Information System from 44 U.S.C., Sec. 3502
NIST SP 800-160 Vol. 2 Rev. 1 under information system from OMB Circular A-130 (2016)
NIST SP 800-160v1r1 under information system from PL 107-347
NIST SP 800-161r1 under information system from NIST SP 800-53 Rev. 5
NIST SP 800-172 under information system from 44 U.S.C., Sec. 3502
NIST SP 800-172A under information system from 44 U.S.C., Sec. 3502
NIST SP 800-18 Rev. 1 under Information System from 44 U.S.C., Sec. 3502
NIST SP 800-30 Rev. 1 under Information System from 44 U.S.C., Sec. 3502
NIST SP 800-37 Rev. 2 under information system from 44 U.S.C., Sec. 3502
NIST SP 800-39 under Information System from 44 U.S.C., Sec. 3502
NIST SP 800-53 Rev. 5 under information system from 44 U.S.C., Sec. 3502
NIST SP 800-53A Rev. 5 under information system from 44 U.S.C., Sec. 3502
NIST SP 800-53B under information system from OMB Circular A-130 (2016)
NIST SP 800-60 Vol. 1 Rev. 1 under Information System from 44 U.S.C., Sec. 3502
NIST SP 800-60 Vol. 2 Rev. 1 under Information System from 44 U.S.C., Sec. 3502
NIST SP 800-171 Rev. 2 under information system from 44 U.S.C., Sec. 3502
NISTIR 7622 under Information System from 44 U.S.C., Sec. 3502
NISTIR 7693 under System
NISTIR 8170 under Information System from 44 U.S.C., Sec. 3502
NISTIR 8286 under Information System from OMB Circular A-130 (2016)

  A discrete set of information resources organized for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information. [Note: Information systems also include specialized systems such as industrial/process controls systems, telephone switching and private branch exchange (PBX) systems, and environmental control systems.]
Sources:
NIST SP 800-128 under Information System from 44 U.S.C., Sec. 3502

  A discrete set of information resources organized for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information. [Note: Information systems also include specialized systems such as industrial/process controls systems, telephone switching and private branch exchange (PBX) systems, and environmental control systems.]
Sources:
NIST SP 800-12 Rev. 1 under Information System from 44 U.S.C., Sec. 3502

  A discrete set of resources that are organized for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information.
Sources:
NIST SP 800-57 Part 1 Rev. 5 under System

  Any organized assembly of resources and procedures united and regulated by interaction or interdependence to accomplish a set of specific functions. Note: Systems also include specialized systems such as industrial control systems, telephone switching and private branch exchange (PBX) systems, and environmental control systems.
Sources:
NIST SP 800-53 Rev. 5 from CNSSI 4009-2015

  Combination of interacting elements organized to achieve one or more stated purposes. Note 1: There are many types of systems. Examples include: general and special-purpose information systems; command, control, and communication systems; crypto modules; central processing unit and graphics processor boards; industrial control systems; flight control systems; weapons, targeting, and fire control systems; medical devices and treatment systems; financial, banking, and merchandising transaction systems; and social networking systems. Note 2: The interacting elements in the definition of system include hardware, software, data, humans, processes, facilities, materials, and naturally occurring physical entities. Note 3: System-of-systems is included in the definition of system.
Sources:
NIST SP 800-53 Rev. 5 from ISO/IEC/IEEE 15288:2015

  Any organized assembly of resources and procedures united and regulated by interaction or interdependence to accomplish a set of specific functions.
Sources:
NIST SP 800-53A Rev. 5 from CNSSI 4009-2015

  An arrangement of parts or elements that together exhibit behavior or meaning that the individual constituents do not. Systems can be physical or conceptual, or a combination of both.
Sources:
NIST SP 800-160v1r1 from Systems Engineering and System Definitions, ISO/IEC/IEEE 15288:2015

  A discrete set of information resources organized expressly for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information.
Sources:
NIST SP 800-221

  An interconnected set of information resources under the same direct management control that shares common functionality. A system normally includes hardware, software, information, data, applications, communications, and people.
Sources:
NIST SP 800-66r2 under information system from HIPAA Security Rule - §164.304

  A combination of interacting elements organized to achieve one or more stated purposes.
Sources:
NISTIR 7622 under System

  A specific IT installation, with a particular purpose and operational environment.
Sources:
NISTIR 5153 under System from ITSEC Ver. 1.2

  See Information System
Sources:
NISTIR 8170 under System

  A discrete set of information resources organized expressly for the collection, processing, maintenance, use, sharing, dissemination, or disposition of information.
Sources:
NISTIR 8286 under System