Plain English Meaning
A position the airplane has ended up in by accident — pointed too far up, too far down, or banked too steeply — that the pilot did not intend and needs to correct right away.
Full Definition
An aircraft attitude that is unintentional, unexpected, and not appropriate for normal flight, typically involving a steep nose-up or nose-down pitch, a steep bank angle, or a combination of the two. Recovery requires a specific sequence of control inputs based on whether the aircraft is nose-high (decreasing airspeed) or (increasing airspeed).