Agnostic as in “I haven’t had an experience to suggest there is a God”.
Atheist as in “my faith-based initiative is to totally believe there isn’t a God”.
There are millions of other things I don't believe in too; it's the default position in many cases.
[1] That's the definition: "a person who does not believe in the existence of a god or any gods" - https://www.merriam-webster.com/dictionary/atheist