Is atheism a religion?

There was a discussion today as to whether or not atheism was a religion.  In 2005, a Wisconsin court ruled that atheism was a religion and an inmate was denied his First Amendment rights to start an atheist group in prison (they came upon this ruling by changing the definition of religion by taking the theistic terms out, lame!).  To me, it isn't, so I took it upon myself to look up some dictionary definitions.  Yes, I am a nerd...it's ok, I've come to terms with that already.  Atheism is defined as the theory or belief that God does not exist.  Plain and simple, to the point. No messin' around with this definition.  Hey,wait a gosh darn minute, that means Buddhism is a form of atheism, interesting.  So, now lets define religion.  This is where it gets tricky.  The definition of religion is: 1. the belief in and worship of a superhuman controlling power, esp. a personal God or gods.  Well, by this definition atheism is not a religion, but neither would Buddhism be one.  The other definition for religion is: 2. a particular system of faith and worship.  Okay, now Buddhism fits as a religion, but I still don't see atheism fitting in here since atheists do not worship.  I also find it interesting that atheism is defined as a theory, yet religion, Christianity, or Buddhism are not labeled as theories, since the definition of faith is a strong belief in God or in the doctrines of a religion, based on spiritual apprehension rather than PROOF.  Anyway, so the I get to thinking, well, maybe atheism is a belief rather than a religion.  Get that dictionary back here!  Belief: 1. an acceptance that a statement is true or that something exists. (actually atheists believe that something doesn't exist),  or 2. something one accepts as true or real; a firmly held opinion or conviction (By the way, the definition of conviction is a firmly held belief or opinion...it goes in circles).  Okay, so atheism may be a belief.  Finally, some headway.  After all of my dictionary learning (and some ibuprofen), my conclusion is that atheism is NOT a religion, contrary to what the Wisconsin court system has ruled.  It is either a belief, opinion, or conviction.  Once I figure out which of these three it is, I will let you know.