atheistical vs atheist

atheistical is not a noun while atheist is a noun.

Word	Noun	Adjective	Verb	Adverb
atheistical	No	Yes	No	No
atheist	Yes	Yes	No	No

As adjectives, atheistical and atheist are synonyms defined as:

atheistical and atheist: related to or characterized by or given to atheism

Other synonyms of atheistical include atheistic.

atheistical (noun)	atheist (noun)
	someone who does not believe in the existence of a god

atheistical (adjective)	atheist (adjective)
related to or characterized by or given to atheism	related to or characterized by or given to atheism
rejecting any belief in gods