"The criteria that a product or product component must satisfy to be accepted by a user, customer, or other authorized entity." (Sandy Shrum et al, "CMMI®: Guidelines for Process Integration and Product Improvement", 2003)
"Those criteria, including performance requirements and essential conditions, which must be met before project deliverables are accepted. " (Cynthia Stackpole, "PMP® Certification All-in-One For Dummies®", 2011)
"A set of conditions that is required to be met before deliverables are accepted." (For Dummies, "PMP Certification All-in-One For Dummies" 2nd Ed., 2013)
"Those criteria, including performance requirements and essential conditions, which must be met before project deliverables are accepted." (Jeffrey K Pinto, "Project Management: Achieving Competitive Advantage" 5th Ed., 2018)
"Formal agreement that a service, process, plan or any other deliverable is complete, accurate, reliable and it meets its specifications" (ITIL)
"The exit criteria that a component or system must satisfy in order to be accepted by a user, customer, or other authorized entity." [After IEEE 610] (Software Quality Assurance)