Open Web Application Security Project (OWASP): A not-for-profit entity that provides unbiased, practical information about application security. This project, supported by a community of corporations, educational organizations, and individuals, produces freely available articles, methodologies, documentation, tools, and technologies to help organizations create secure web applications.

Operating Expenses (OPEX): The costs a business incurs through its normal operations, including rent, equipment, inventory, staffing, transportation, sales commissions, and advertising. These recurring expenses are essential for running the business and impact its profitability.

Operating System (OS): The primary software that manages all the hardware and other software on a computer. It performs a variety of functions, including managing memory, processing tasks, accessing the hard drive, interpreting commands from a keyboard or mouse, and sending output to a display screen.

Operational Audit: A detailed analysis conducted to assess an organization's internal operations in terms of effectiveness, efficiency, and adherence to policies and procedures. It involves reviewing day-to-day activities and processes to identify potential areas of improvement or detect any misconduct.

Operational Controls: A type of security control that focuses on the day-to-day operations of an organization. It includes procedures, policies, and standards that are designed to prevent, detect, and respond to security incidents. Examples of operational controls include access controls, change management, and incident response plans.

Operational Level Agreement (OLA): An agreement that outlines how various departments within an organization collaborate to meet service level requirements (SLR) for internal or external customers. OLAs typically support Service Level Agreements (SLAs) to ensure all supporting processes are synchronized to deliver a specified level of service.