In your example, I think Bob is doing something unrelated to rationalist Taboo.
In the actual factual game of Taboo, you replace a word with a description that is sufficient to tell your team what the original word is. In rationalist Taboo, you replace a word with a description that is sufficient to convey the ideas you were trying to convey with the original word.
So if Bob tries to taboo "surprise" as "the feeling of observing a low-probability event," and Alice says "A license plate having the number any particular number is low probability - is it surprising?," Bob should think "Oh, the description I replaced 'surprise' with did not convey the same thing as the word 'surprise'. I need to try tabooing it differently."
This works better when you're trying to taboo the usage of a word in a specific context, because the full meaning of a word is very very complicated (though trying to make definitions can still be a fun and profitable game, I agree), but when you look at how you've used it in just one sentence, then you have some hope of pinning down what you mean by it to your satisfaction.
The problem with Rationalist Taboo is that it was invented to make others clarify their thoughts, not to clarify your own.
Here's how it usually goes wrong: "You can't explain the color red to me? Hahaha, I've dissolved the idea of qualia! They are just an illusion!" No, silly, your opponent's failure to define X doesn't prove you right about X. You're just turning yourself into a person who declares all hard-to-define ideas illusory in order to stop thinking. Is that what you really want?
Focusing on the meanings behind words is a great idea and I'm happy that we have it in this community. But asserting that a word is useless should only be done with caution! Even misguided words still come from a millennia-long optimization process, like butterflies, and there are secrets to learn from the swirls on their wings. To that end, instead of Rationalist Taboo, I prefer to use good old steelmanning:
Alice: Can you explain what you mean by "surprise"?
Bob and Carol in unison: Observing a low probability event.
Alice: This morning I saw a car whose license plate said 8713, but it didn't surprise me at all!
Bob: Hmm, it looks like my concept of "surprise" was misguided. I won't use the word from now on.
Carol: Hold on. The word "surprise" might lead to some other nontrivial concept that's useful in its own right. Maybe it's about description length? Or logical uncertainty? I'll try to formalize...
Carol wins the exchange, because Bob dissolved a word prematurely and gave up the chance to think an interesting thought. These days I try to be more like Carol, and when I hear a seemingly misguided word like "essence" or "emergence", my first instinct isn't to kick it when it's down, but to steelman it and rescue whatever is worth rescuing.
What Taboo gets right is that words are mere handles, and meanings are the only part worth discussing; but when you try to capture a word, there will always be leftover meanings, often more complex and interesting than the one you caught. That's what Taboo gets wrong.
