Formal declaration by a Designated Accrediting Authority (DAA) or Principal Accrediting Authority (PAA) that an information system is approved to operate at an acceptable level of risk, based on the implementation of an approved set of technical, managerial, and procedural safeguards. 

Source: CNSSI-4009

Merriam-Webster Online Thesaurus
accreditation (noun)
the granting of power to perform various acts or duties
accreditation, authorization, delegation, empowerment, license ( licence), mandate
commendation, consignment, entrustment; facilitation, fostering, promotion; commanding, directing, ordering
Accreditation is a process of review and recognition by an external body that an organization, institution, program, or service meets established standards of quality and performance. It is a voluntary process that organizations undergo to demonstrate that they meet certain standards of quality and performance.