Is atheism a belief?

[Bucky Ball]

My word but you are wrong a lot.  Atheism is a belief in the same way that not collecting stamps is a hobby or bald is a hair colour.

---

It's actually irrational to believe the sun exists.  We have more than sufficient evidence to accept the existence of the sun, just like I have more than sufficient evidence to accept the existence of the chair I'm sitting in or the keyboard I'm typing this post with.

Belief only comes into play when there is insufficient evidence for acceptance, or with religion, an utter lack of evidence at all.

If someone says:

"I believe the earth's orientation is flat "

and I say:

"I believe the earth has a spherical orientation."

Is my statement to them irrational?  Where did you get the idea that "belief" is irrational?  Do you have an objective source for this?

You're equivocating the word" belief". 
Used in the common way "it is my position ("belief") that the Earth is not flat" (based on a myriad of evidence)  if FAR different than invoking the concept of religious "faith" belief, based on no evidence.