ICANN accredited domain registrar means domain registrars that are accredited by ICANN organization, the organization that manages the international domain name system.
To be ICANN accredited registrar, the domain registrar must adhere to the terms and conditions of this accreditation.
ICANN terms and conditions include maintaining a high level of the quality of services, protection of customer privacy, keeping the registry clean by protecting from cyber-squatting, and more.