In atheism terminology, atheism synonyms, as contrasted to theism synonyms (e.g. believer), are terms that generally mean disbelief and or denial in the existence in god, which, barring detailed clarification, include: free thinker (Molyneux, 1697), heathen, radical, doubter, unbeliever (Mammon, 1782) or non-believer, materialist, nihilist, secularist (Holyoake, 1851), humanist, bright (Paul Geisert, 2003) (Ѻ), godlesss, and zerotheistm (Thims, 2015), or combinations thereof, e.g. "secular humanist" (Warraq, 1995), "secular naturalism" (Edd Doerr, 2014), "materialistic atheist", etc. [1]

See also
Atheism clarifiers | Radical atheist, militant atheist, extreme atheist, etc.
Atheism types | Spinozist, Hobbesian, Nietzschean, etc.

References
1. (a) Hecht, Jennifer M. (2003). Doubt: A History: The Great Doubters and Their Legacy of Innovation from Socrates and Jesus to Thomas (Bright, pg. 483). HarperOne.
(b) Joshi, S.T. (2014). The Original Atheists: First Thoughts on Nonbelief. Prometheus Books.

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