Plain English Meaning

A controlled way of making the airplane descend faster, or stay lined up with the runway in a crosswind, by deliberately flying it slightly sideways using opposite rudder and aileron at the same time.

Full Definition

A deliberate flight maneuver in which the pilot cross-controls the airplane — applying aileron in one direction and opposite rudder — to fly the aircraft slightly sideways through the air. This increases drag and steepens the descent path without increasing airspeed, and is used to lose altitude or to compensate for a crosswind on landing.