Plain English Meaning

An approach where the airplane isn't where it should be, doing what it should be doing, at the speed it should be doing it. Either things aren't settled and steady (unstable), or the airplane is flying too slowly (slow), or both — and that combination makes a safe landing much harder.

Full Definition

Approaches in which the airplane is not on a stabilized path to the runway by a defined point — meaning airspeed, descent rate, configuration, power, or alignment are not within target ranges — and/or the airspeed is allowed to decay below the target approach speed, increasing the risk of high sink rate, loss of control, or an inability to arrest the before .