From SKYbrary Wiki
An aerodynamic condition, during a turn, where the tail of an aeroplane moves away from the centre of the turn or tends to follow a path which is outside that followed by the nose.
To maintain coordinated flight during a turn, blended aileron, rudder and elevator inputs are required. Too much rudder input will result in the tail of the aircraft being forced outside of the arc followed by the nose, a condition referred to as "skid".
Approaching the stall speed of the aircraft, a skid during a turn can result in the inside (lower) wing stalling first which would tend to tighten the turn and could lead to a spin. In the traffic pattern, this situation is often referred to as a "final turn stall" and can occur when a pilot misjudges the turn from base leg to final approach and, either intentionally or subconsciously, applies additional rudder in an attempt to tighten the turn to avoid overshooting the extended runway centreline.