I don't have a reference text available to back me up, but I'm pretty sure it's called high-speed buffet.
In the 747, getting aileron buzz at 350 IAS and M0.86 around FL320 (and a TAS of 530+ knots) isn't what I would call "Low Speed."
Perhaps some think of it as "Low Speed" because at a relatively "low" Indicated Speed, you are getting the effects of something at Mach 1.
Again, semantics. I can see a case for calling it either. But in the case of where I accidentally did it (in Mach-mode in a descent instead of transitioning to IAS), the Capt's response was "You're too fast...slow down!!"