About Registrar Accreditation- "ICANN is a technical coordination body. Our primary objective is ensuring the stability of the Internet's system of assigned names and numbers. This objective is furthered by the requirement that every business desiring to become a registrar with direct access to ICANN-designated top-level domains must first become accredited for this purpose by ICANN."
A Registrar that has been certified as meeting certain minimal criteria to act as a Registrar for a specific TLD. This term is almost solely used when referring to Registrars that have been certified by ICANN.
A Registrar that has been accredited by auDA as meeting certain minimum criteria to act as a Registrar for a specific 2LD.
A Registrar (retailer for ENUM) that has been accredited having met certain minimum criteria to act as a Registrar.
A domain registrar that has been certified to meet a list of criteria determined by ICANN (The Internet Corporation for Assigned Names and Numbers). An "accredited registrar" is typically one that has been accredited by ICANN.
An accredited registrar, also called an Accredited Certification Body (CB), are organisations certified to be qualified by a national body to perform audits to a standard (e.g. ISO 9001) and to register the audited facility as meeting these requirements for a given standard.