(Not to be confused with the noun 'atheist', which means 'somebody who does not believe in god(s)'.)
Athy Person: I'm athiest! I know that the bible is false and that there is no God. SCIENCE proves it, so it must be true! I don't need to talk about it, my faith lies in SCIENCE.
Legitimate Atheist: Yes, you are quite athy (speaking to Athy Person). I would love to discuss religion with you (speaking to Theist).
Athy Person: Thank you.