What is windshear?

Windshear refers specifically to a sudden change in wind speed and/or direction over a short distance in the atmosphere. This phenomenon can occur at various altitudes and is particularly significant during takeoff and landing phases of flight, as it can dramatically affect aircraft performance and control. Pilots must be aware of windshear because it can lead to hazardous flying conditions, particularly during those critical phases of flight where a rapid change in wind conditions can lead to loss of lift or unexpected changes in flight path. Recognizing windshear helps aircrew make informed decisions and execute safety procedures to ensure a safe flight. The other options do not capture the sudden nature of windshear, either implying gradual changes or consistent conditions, which are not applicable to this specific atmospheric phenomenon.