What does it mean if a landing is described as 'unstable'?

An unstable landing indicates that the aircraft is unable to maintain a safe and controlled descent profile as it approaches the runway. This can occur when the approach speed is improper—either too high or too low—which prevents the pilot from establishing a safe landing trajectory. An approach that is too fast may lead to difficulty in landing within the desired landing zone, while an approach that is too slow could result in a stall, making it critical for pilots to ensure they are at the correct approach speed. When pilots recognize that an approach has become unstable, standard procedure often involves going around and attempting the landing again, ensuring the aircraft is in a safe configuration and alignment for landing.