1. A disbeliever in the existence of a God.

2. Atheistical.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• athetism,
• athesism,
• athet,
• atheus,
• atist,
• atest,
• athesis,
• aitheist,
• atheisim,
• athiest,
• athieism,
• athesist,
• fathest,
• aethist,
• athers,
• batherst,
• atheis,
• arthrist,
• aitheists,
• athists

• attest,
• attestant,
• attester,
• attestator,
• attestor,
• atheistic,
• attested.

The adjective form of the word "atheist" is "atheistic".

The plural of the "atheist" can be the "atheists".

The singular of the "atheist" can be the "atheist".