What is the meaning of Atheism?

A non-belief in deities.

Belief that no deities exist (sometimes including rejection of other religious beliefs).

A lack of belief in deities, or a belief that there is insufficient evidence to believe in a god.

Absence of belief that any deities exist (including absence of the concept of deities).

Absence of belief in a particular deity, pantheon, or religious doctrine (notwithstanding belief in other deities).

Absence of belief in the One True God, defined by Moore as personal, immaterial and trinitarian (thus Islam, Judaism and unitarian Christianity), as opposed to monotheism.

A rejection of all religions, even non-theistic ones.

Source: wiktionary.org