Final answer:
The International Organization for Standardization (ISO) is the organization to turn to for the official definition of the OSI model.
Step-by-step explanation:
The organization to turn to for the official definition of the Open Systems Interconnection (OSI) model is the International Organization for Standardization (ISO).
The ISO is an independent, non-governmental organization that develops and publishes international standards for various industries and sectors, including technology.
The OSI model is a conceptual framework that helps explain how different computer systems communicate with each other by breaking down the process into seven layers, each with specific functions and protocols.