atheistPronunciation: /ˈeɪθɪɪst/Translate atheist | into French | into German | into Italian | into Spanish Definition of atheist noun a person who disbelieves or lacks belief in the existence of God or gods:he is a committed atheistDerivatives atheisticPronunciation: /-ˈɪstɪk/ adjective atheisticalPronunciation: /-ˈɪstɪk(ə)l/ adjective atheist in other Oxford dictionaries Definition of atheist in the US English dictionary