Plain English Meaning
Tiny liquid raindrops that are colder than freezing but still liquid in the air. The moment they touch the aircraft, the runway, or the ground, they turn into ice.
Full Definition
Drizzle composed of very small liquid water droplets, typically less than 0.5 millimeters in diameter, that fall to the surface in a supercooled (below-freezing) liquid state and freeze on contact with objects whose temperature is at or below 0°C. Reported as FZDZ in aviation weather products.
Context Anchor
Pilots encounter this term in weather reports, forecasts, and discussions, often shown as FZDZ, the - code for freezing drizzle.