AI is a broad, unspecific term. It's like the term "plants" - it covers everything from grass to giant redwoods but we have more specific terms for the subcategories for a reason. If we just refer to all life that photosynthesizes as plants then nobody knows which plant you're talking about. Nowadays when someone speaks of AI it's relatively safe to assume that they're talking about one of the multimodal frontier models (that are not only LLMs) but it's sloppy, imprecise use of language and it will lead to people talking past each other.

In the classical sense AI refers to a system capable of performing any cognitive task typically attributed to a human. Under this definition, even an Atari chess engine is an AI. However nowadays the meaning has shifted a little and the term typically refers to a system that has been trained with a bunch of data.