If your definition of an atheist is a person who believes gods don't exist, if a person told you "I am an atheist but I don't believe gods don't exist, I am just not a theist" would you tell him that he's not an atheist? You would have to wouldn't you, otherwise you would have changed your definition...
I think you are a little bit confused about what you actually asked. What you actually asked has
nothing to do with 'definitions'. As I said back in my first post 'In average conversation we don't try to be entirely logically consistent and objectively approach the conversation as a form of scientific or philosophical analysis.'
You are asking what meaning is communicated by the word atheist when used in normal conversation: "When a person tells you he/she is an atheist, what do you think that tells you?"
This is asking what
subjective meaning is communicated, which is a process by which you construct a range of both denoted and connoted meaning from knowledge, experience, intertextual references, etc.
Language in practical everyday use is very different from crafting philosophically accurate language for normative purposes (and also from arguing on RF about concepts). I've already told you I'd make assumptions beyond the scope of the actual word. I'd assume what is true of most atheists I know, and revise my opinions later if evidence conflicted my initial assumption. That's what we do when we communicate.
I'm trying to be honest by acknowledging the irrational assumptions we make from language in everyday usage. We all do it, whether we realise it or not. Where I live I would also assume that the person was middle class and university educated, even though I have atheist friends who are neither. It just happens that most atheists in this society happen to share these characteristics, so, heuristically, it is beneficial for us to make such assumptions unless we have evidence to suggest they are wrong (which is why, for example, appearance would also affect my assumptions).
You don't aim for perfection, but best fit.
If you ask me 'what can you tell with 100% certainty if someone tells you they are an atheist' then I would say nothing. You could tell things with a very high degree of certainty, but not 100%. But you didn't ask that question so I gave you an accurate reply to the question you asked.
Why bother to create a thread about how people subjectively interpret a word then berate several posters for not subjectively interpreting it in the way you wish they had subjectively interpreted it?