Is atheism a belief?

[Bucky Ball]

Whenever I say that atheism is based on belief just like theism is I get a strong rejection from atheists. 
Some give me these twisted definitions while others claim that i cannot be agnostic without being an atheist.

So I want to start by getting the definition correct.
Am I right in saying atheists "believe there are no Gods" or "don't believe there are Gods"?
Am I right in saying atheism is based on belief? If yes then why do so many atheists reject this?
If not then Why? What is it then based on?

Both.

An Atheist can be:

1-Some one who knows God does not exist.
2-Some one who believes God does not exist.
3-An atheist can also be someone, who doesn't believe or know one way or the other. His lack of belief one way or the other, would still classify him as an atheist, since he doesn't posses a belief in God, like the other two examples.

Some people might know I'm not single.
Some people might believe I'm not single.
And some people might not believe or know one way or the other.

What they all have in common, is that they a lack a belief in that I'm married.

Atheism is label that can incapsulate all three under one umbrella.

It's very funny that non-atheists think they can tell atheists how they think.

There are those who have or take no position at all with respect to the subject.
They are not a-theists, as for them, theism is meaningless.
A-theism is a specific position with respect to another specific position. No theism.
A-theism is not a general position.  

Are the Piraha https://en.wikipedia.org/wiki/Pirah%C3%A3
atheists ? They have no conception of a god.

If someone does not recognize the specific position (theism) as coherent, there is no position to lack, (for them).
Therefore igthesim is a far more accurate label, for them.