High speed stall amd mach
Great points, JT the Moderator.
It could be that the term bandied about refers to mach effects such as I related from the Yeager discussion.
If we exceed the "critical" mach, we can see things like aileron reversal, nose tuck, flutter, etc. All these bad things due to the shock wave moving back along the stabilizer or main wing and preventing the normal control surfaces at the rear of the wing or stabilizer from acting normally.
Another way to get into trouble near the critical mach is to rapidly change your AoA. The shock wave will move along the chord of the wing and have the same results as exceeding the critical mach. This more closely resembles the "high speed stall" phenomena described by JT the Mod.
Unless you are driving a supersonic design, pulling back the power is usually sufficient, as you are already experiencing a lotta drag. If in a dive, that may not be enough and spoilers or other drag devices might also be required. As most airliners have swept wings, they are more tolerant of mach effects than the old straight wings, so I am not too worried about mach-induced control problems for the present scenario we are discussing/analyzing.