Plain English Meaning

Tiny drops of water that are still liquid even though they are colder than freezing. As soon as they hit something solid, they turn to ice almost instantly.

Full Definition

Liquid water droplets that remain in liquid form at temperatures below 0°C (32°F). When these droplets strike a surface such as an aircraft, they freeze on contact, producing structural icing.

Context Anchor

Seen in cloud, weather, and icing discussions, especially when an aircraft is flying through visible moisture in below-freezing temperatures.

Derivation

‘Supercooled’ means cooled below the normal freezing point without actually freezing. Pure water in still air can liquid well below 0°C because freezing needs something to the ice forming — like a surface or a particle. An aircraft flying through such droplets provides exactly that trigger.