Not a definition of intelligence, but something I often come back to is what it does at rest.

To the best of my understanding of how LLMs work, if you’re not feeding the thing inputs, the program is doing absolutely nothing. It isn’t curious and doesn’t seek new information or stimuli. It effectively is just on pause until the next prompt. There is nothing akin to an inner monologue or thought process happening in absence of what is fed to it.

I’m not up on all of the epistemology or theory of mind type stuff, but I’d imagine some might argue about that distinction in humans; we are always processing input in some form as the input from our senses is never shut off until we’re dead. But I think the “at rest” case is a relevant distinction that does get at motivation and real thought born of real intelligence.