An engineering discipline whose responsibility is creating and executing an interdisciplinary process to ensure that the customer and all other stakeholder needs are satisfied in a high-quality, trustworthy, cost-efficient, and schedule-compliant manner throughout a system’s entire life cycle.
Sources:
NIST SP 800-53 Rev. 5
NISTIR 8062 from What Is Systems Engineering
NISTIR 8062 under Systems Engineering from What Is Systems Engineering

  Interdisciplinary approach governing the total technical and managerial effort required to transform a set of stakeholder needs, expectations, and constraints into a solution and to support that solution throughout its life.
Sources:
NIST SP 800-160v1r1 from ISO/IEC/IEEE 24765:2017
NISTIR 8062 from ISO/IEC/IEEE 24765
NISTIR 8062 under Systems Engineering from ISO/IEC/IEEE 24765

  A transdisciplinary and integrative approach to enable the successful realization, use, and retirement of engineered systems, using systems principles and concepts, and scientific, technological, and management methods.
Sources:
NIST SP 800-160v1r1 from Systems Engineering and System Definitions