What does "wind shear" signify?

Wind shear signifies a sudden change in wind speed or direction at different altitudes, and this can have significant implications for aviation. It often occurs in various weather conditions, such as during thunderstorms, when the winds can shift dramatically over short distances vertically or horizontally. This shifting wind can impact an aircraft's performance, especially during takeoff and landing, where a consistent airflow is critical for safety and stability.

Understanding wind shear is crucial for pilots, as it can lead to dangerous situations such as loss of control if not anticipated. The other options describe conditions or phenomena that do not accurately represent wind shear, such as consistent wind speeds or stable wind conditions, which are the opposite of what wind shear entails. Additionally, while mountain-induced turbulence is a valid consideration in aviation, it does not specifically define wind shear.