Plain English Meaning
Special airspace whose rules are written into federal law. Pilots must obey it. The two types are Restricted Areas (entry only with permission) and Prohibited Areas (entry not allowed at all).
Full Definition
A category of special use airspace that is established by formal rulemaking and codified in the Code of Federal Regulations (14 CFR Part 73). It includes Restricted Areas and Prohibited Areas, where flight is either restricted under specified conditions or forbidden outright because of activity inside the airspace that poses a hazard to aircraft or because of national security needs.
Context Anchor
Seen when planning an instrument , reading , or reviewing that pass near or restricted areas.