High voltage electricity refers to electrical potential large enough to cause injury or damage.
There are no real voltage level for high voltage per definition. If it can hurt or kill humans or animals then it is high voltage. That is all voltages that draw more than 30mA through the standardised human body or a animal.
High voltage per the definition of >1000V is the voltage level when the current starts to move as a corona effect, air is ionized and discharge length is 1000V/cm.
In Sweden we did name this from the year 1909 as Starkström (kind of ”strong current” in english) that had the definition of ”all currents that is dangerous for humans and animals”. And in the regulations (was called the “The blue book” because of it’s color) from the electrical agency had three chapters A (common rules), B with safety rules for voltage level under 1000V and chapter C with the safety rules when at voltages over 1000V.
But the definition of ”strong current” was in chapter A so it applied for both chapter B and C. Then someone invented the EU...
The problem is that I am not aware of any english speaking country that made the definition of “strong current” as the definition of dangerous and not dangerous. Instead high voltage became the definition in English.