1. Information representing the sensitivity of a subject or object, such as its hierarchical classification ("confidential," "secret," "top secret") together with any applicable nonhierarchical security categories (e.g., sensitive compartmented information, critical nuclear weapon design information. ) Synonym security classification. 2. The marking bound to a resource (which may be a data unit) that names or designates the security attributes of that resource. Note: The marking may be explicit or implicit.