The lack of a universally agreed upon definition does imply the lack of an objective definition. And it also does not imply there isn't a general definition that most people agree on that works in most cases.

Almost all words have different meanings when you get into a specific niche. "Elastic" in casual contexts means stretchy, but in physics contexts, specifically describes a materials ability to return to it's prior state after being stretched. But if I said "Elastic" lacks a definition in physics entirely, we wouldn't run around saying "nothing is elastic".

Yet for some reason people do that exact thing with Vegetables/fish.