They may be trying to differentiate between high temperature as "fast", like in this case, and high pressure as "hard". Though both can lead to a particle kinetic energy above the Coloumb barrier, in the former case the time between collisions will be lower (AFAICT), which may be important. I'm not a plasma guy though.

Sorry, I should've been much clearer, that was really badly worded as I was distracted also doing my day job :) As a sibling comment pointed out, I wasn't using any specific terminology as I was trying to talk at a layman level. There's not really a difference. I should've said 'hard enough and fast enough'.

Conceptually, there's two main methods of fusion - inertial confinement, and magnetic confinement.

In inertial confinement, lasers are shot at the plasma to squeeze it together so the pressure (and thus temperature) increases until fusion occurs. This is also what happens in stars, except they use gravity not lasers. Conceptually, this is what I alluded to when pushing it 'harder'

In magnetic confinement, the pressure/temperature is increased by shooting electrical currents through the plasma among other techniques that i'm not as familiar with. The volume hasn't really decreased, but the kinetic energy and pressure of the plasma has increased so it's the same principle, but this is conceptually what I alluded to when i said pushing it 'faster'.

In either sense, the idea is to somehow increase the plasma temperature which increases the kinetic energy of the particles enough that they overcome the electrostatic barrier. It was just really badly worded by me and I apologise for that!

In my general understanding of these things:

Fast -> High kinetic energy since they won't acquire mass this is basically speed

Hard -> More attempts to make it happen (higher particle interaction)

But I might be wrong since plasma is weird stuff.

I guess hard is something inside the star where matter is compressed by gravity and fast is when you're accelerating matter. In the end it's the same, only you can't use gravity for small reactors to replicate star technology yet, so you must accelerate particles.

SciFi likes to talk about antigravitation. But supergravitation would be cool as well :)

GP isn't using standard terminology, but I would presume "hard" was in reference to more mass, which results in higher kinetic energy at lower temperatures.