Absence of belief in a particular deity, pantheon, or religious doctrine (notwithstanding belief in other deities).
Absence of belief that any deities exist (including absence of the concept of deities).
Rejection of belief that any deities exist (with or without a belief that no deities exist).
Belief that no deities exist (sometimes including rejection of other religious beliefs).
An offshoot of a larger religion or denomination, usually and especially one with unorthodox or extreme political and/or religious beliefs.
A group following a specific ideal or a leader.