From the given list, choose tire one word substitute for 'one who does not believe in God'

atheist

The word that best substitutes for "one who does not believe in God" is atheist.

• Agnostic means "a person who believes that it is impossible to know whether or not God exists."
• Atheist means "a person who does not believe in the existence of God."
• Theist means "a person who believes in the existence of God."
• Entrepreneur means "a person who sets up a business or businesses, taking on financial risks in the hope of profit."

The word "atheist" is the best fit because it conveys the idea of a person who does not believe in God, regardless of whether or not they believe that it is possible to know whether or not God exists.