CAVOK

Definition

Acronym of ceiling (or clouds) and visibility [are] OK, a weather term, specific to an airport, used when conditions at the airport include visibility of at least 6 statute miles, no clouds below 5000 feet or minimum sector altitude (whichever is higher), and no hazardous weather conditions (cumulonimbus clouds, thunderstorms, precipitation, shallow fog, or low drifting snow) near the airport.