Expanding on the other answer...
A loss of controlled flight (departure) is what happens when the aircraft is moving in an uncontrolled manner (on any one or all axis). For example in the video that the other answer linked, the departure from controlled flight happens when the aircraft exceeds its operating envelope and begins uncommanded movement in any axis, in this case when the pilot yanks back on the stick and the aircraft yaws uncommanded (like a "boot full of rudder" as the person in the video comments).
This is why an aircraft can depart controlled flight in individual axis while retaining control in others. You can intentionally make an aircraft depart controlled flight (spin for example) and if the control surfaces still have enough authority, it can be recovered (altitude withstanding). You aren't really "in control" but you are coaxing the aircraft back into the flight envelope.
If you don't have enough control authority to get back into the flight envelope, or altitude, this is otherwise known as a crash... Some aircraft cannot be recovered from maneuvers like spins (Cirrus SR-20/22 for example, not certified to at least).
So, controlled flight is defined as providing control inputs without uncommanded movement on any axis (significant, for example just using ailerons may result in yaw). Any departure from controlled flight is uncontrolled flight, even if you regain control later.