Is no Religion a Religion.

[Mister Agenda]

Theism=believes in at least one God or god.

Doesn't that definition apply more to deists? I took theism to mean belief in and worship of a personal god, (which is religion), and atheism do be the negation of theism.

It doesn't exclude deists. There's no requirement in the definition of theism that one worship a god one believes exists. A person can be a 'mere theist' who believes some sort of God exists (not necessarily a non-interfering deistic one) without being too worried about the nature of that God. I'd say a lot of agnostic theists fall under that category.