In a bit more detail than Starvid: conventional fast trains going on upgraded but conventional lines (shared with freight and local passenger), and reaching the top speed only on short sections. In the US, the Acela on the East Coast already fits that bill, but much slower trains further west (100 mph or slower) are also dubbed 'high-speed'. But the X-2[000] service in Starvid's home country Sweden is also such a thing.

On the other hand, what speed shall count high-speed, is not that straightforward. The first true high-speed system, the Japanese Shinkansen, started with 200 km/h. Even today, many Shinkansens only do 240 km/h, close to the Acela's top speed. The French TGV started at 260 km/h. The German ICE started with 250 km/h, though 280 km/h was permitted for late trains.

_{*Lunatic*, n.
One whose delusions are out of fashion.}