Jim Herrick quotes:

"Agnostic" is a much more recent word than "atheist", coined by Thomas Huxley in 1869 to mean "without knowledge of God" and acquiring the usage of "being doubtful about the existence of God."

An argument frequently used by believers [is] to force unbelievers to soften their terms by accepting their opponents' definition; "Atheist" means without a concept of God that is logically convincing, not with proof that God does not exist.

"Atheist" is quite clear in its meaning of "somebody without a belief in God." It is more complex in its usage since it has often been used to blacken anyone with the slightest doubt about the teachings of religion.