Ask someone this yes/no question:
Do you believe God exists?
If they say “Yes” - they are a theist. If they say anything else (“No”, “Maybe”, “Don’t know”) then they are an atheist.
I think its that simple.
Ultimately, we are all agnostic about everything except consciousness. And to keep bringing that up is to confuse people. Matt Dillahunty first nailed this home for me - we don’t have 100% knowledge, and we don’t care to; good enough knowledge, 95% knowledge, whatever the percent - that is what we use in our daily conversations.