Thank you for the question on idolatry, “What if a person is an atheist and doesn’t worship anything, nor God, neither Gods? Does it mean that they are not idolaters according to the Bible?”
Here are some thoughts for one’s consideration about idolatry:
A. Idolatry can be define as the the worship of someone or something other than God as though it were God. To answer the above question one also has to define worship.
Merriam Webster Dictionary says this, “1: to honor or show reverence for as a divine being or supernatural power 2: to regard with great or extravagant respect, honor, or devotion// celebrity worshipped by her fans.”
B. If a person places the highest value on an object or upon a person, that could be consider “worship” of that thing. Some people worship or are ardent followers of a celebrity, following their tweets or on Instagram. Some people accept Bart Ehrman’s writings as almost or equal to “Scripture” even though he may not place that value on it. Do they see him more than atheist apologists? To be sure Christians may do that as well as they follow a certain speaker and are devoted to him or her. What she/he says is almost like “Scripture.”
Every person treasures or values something above everything else. That “thing” is their “god” for they seek for it with their whole being. They give everything to that cause or to obtain that position.
C. Every person seeks purpose in their life. Jesus stated that what a person seeks becomes their treasure or idol. I believe every human being seeks something in their life and are consume in driving to obtain or to possess it. Whether one finds fulfillment upon obtaining is uncertain.
I do believe that there is “hole” in each person’s life in which that person is seeking to fill it with something or someone. God made humans to have a personal relationship with him. Can man be completely satisfied apart from God? King Solomon says that everything is vain on earth and the pursuits of it is empty at the end in his writing of Ecclesiastes. He tried everything that was available to him in his time period and found them lacking and meaningless.
SUMMARY: Every human being searches or cherishes something that is greater than oneself. That quest can be considered idolatry for that is what that person’s desires more than anything else.