Visual flight rules
From Glossary of Meteorology
visual flight rules
(Abbreviated VFR.) A set of regulations set down by the U.S. Civil Aeronautics Board (in Civil Air Regulations) to govern the operational control of aircraft during visual flight.
The abbreviation VFR is seldom used to denote the regulations themselves, but is popularly used to describe the weather and/or flight conditions to which these rules apply.
