Plain English Meaning

A VFR pilot accidentally flies into clouds, fog, or weather where they can no longer see outside well enough to fly visually, and must use the cockpit instruments to keep the airplane upright and under control.

Full Definition

An unplanned entry into instrument meteorological conditions (IMC) by a pilot operating under visual flight rules (VFR), in which outside visual references are lost and continued flight requires reliance on flight instruments. IMC exists when visibility, distance from clouds, or ceiling falls below , leaving without a usable .