Атеизм
(франц. atheisme, от греч. а - отрицательная частица и theos - бог; буквально - безбожие), отрицание существования бога, каких-либо сверхъестественных существ и сил и связанное с этим отрицание религии.

(Большая Советская Энциклопедия)

Более общее и более путанное определение:

Atheism, defined as a philosophical view, is the position that either affirms the nonexistence of gods[1] or rejects theism.[2] In its broadest definition, atheism is the absence of belief in deities, sometimes called nontheism.[3] Although atheists are commonly assumed to be irreligious, some religions, such as Buddhism, have been characterized as atheistic.[4][5]

Many self-described atheists are skeptical of all supernatural beings and cite a lack of empirical evidence for the existence of deities. Others argue for atheism on philosophical, social or historical grounds. Although many self-described atheists tend toward secular philosophies such as humanism[6] and naturalism,[7] there is no one ideology or set of behaviors to which all atheists adhere.[8]

The term atheism originated as a pejorative epithet applied to any person or belief in conflict with established religion. With the spread of freethought, scientific skepticism, and criticism of religion, the term began to gather a more specific meaning and was sometimes used as a self-description by atheists.

(Wikipedia)