What does the term 'crosswind' refer to in aviation?

The term 'crosswind' in aviation specifically refers to a wind that is blowing perpendicular to the aircraft's flight path. This type of wind can significantly affect an aircraft's control, especially during takeoff and landing. Pilots must be aware of crosswinds, as they can cause drift and require adjustments to the aircraft's approach to maintain a straight flight path relative to the runway.

In the context of aviation operations, understanding the nature of crosswinds is critical for safe maneuvering. For instance, when landing in a strong crosswind, pilots utilize certain techniques such as the crab method or side slip method to align the aircraft with the runway while still managing the wind effect.

The other options describe different wind behaviors. Wind flowing parallel to the flight path does not create challenge during approach or landing, and wind that blows at an angle to the runway may not necessarily indicate a critical crosswind condition depending on the angle. Additionally, winds associated with storm conditions refer to phenomena that may be related but do not define the crosswind concept specifically.