When Bob comes up with the word “squee-bear”, he knows a squee-bear when he sees one, but he might not yet have worked out exactly what makes it a squee-bear to him. He might not yet be able to offer a definition. And if Bob talks about squee-bears to Alice and Charlie, they might start using the word in slightly different ways from Bob.

This sort of thing happens in the history of science, for instance. People start talking about “planets” (originally meaning “wandering stars”) or “atoms” (“indivisible units”) and then only later does a community of speakers nail down exactly what they mean by “planet” or “atom” and it turns out that planets aren’t stars and atoms aren’t indivisible.

For people, language use is axiomatic — and messy. We talk about things even when we don’t know what they are; we talk about things even when we’re not 100% sure what we mean.

Definitions come later.

People run into problems when they put definitions ahead of reality. That’s what we see, for example, when creationists try to talk about “species”, or transphobes about “woman”. They act as if they want a simplistic definition they learned as a child to apply forever, in all context, and for anyone who disagrees to be just wrong. But that’s not how language works and it’s not how reality works.