If the evaluation of a position were only about the raw material count, the game would be rather dull.

The "oh shit" move doesn't necessarily make your position suddenly way worse, it can be just the moment when you realize how much better your opponents position has been for a while.

Sure.

Hence why I talked about the feeling you get when you realise you have mis-evaluated rather than trying to define it precisely.

From the OP:

> But when AlphaZero plays, and you watch Stockfish's score, the reason it wins is that it makes moves Stockfish thinks is poor, so it rates AlphaZero's moves poorly, and then all of a sudden it has an oh shit! moment when it realises that AlphaZero is actually ahead, and its score jumps. It's really a look inside the computer's head while it's being beaten by a better player.

Sure - you get that feeling from blunders too. But take a look at the Stockfish vs Alpha Zero games - Stockfish doesn't blunder. It it just outplayed: https://www.chess.com/news/view/updated-alphazero-crushes-st...

If you watch from here in game one you can see the "oh shit" moment, as Stockfish's evaluation drops from +1 to even to -1: https://youtu.be/Q5EPqM8gS7k?t=255

There were blunders in the first round of games. I remember this vividly because I went through all the games with the exact same version of Stockfish with the same time controls and it thought some of its own moves were blunders. This is partly why people were so puzzled by the setup that led to this.

Most people I've seen talking about chess use "blunder" to describe a mistake with almost-immediate consequences like the loss of materiel.

A move that worsens the position in a way that's not so immediately obvious might be called a 'mistake' or 'inaccuracy'

By these standards, it's quite possible for a game between humans to be won or lost without a blunder on either side.