1. a set of beliefs concerning the cause, nature, and purpose of the universe, especially when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs.
2. a specific fundamental set of beliefs and practices generally agreed upon by a number of persons or sects: the Christian religion; the Buddhist religion.
I didn't get far into this thread when I noticed a very limited deinition of "religion". The definitions here are much better. The poster also left out a key part of the Webster defintion which says:
: a personal set or institutionalized system of religious attitudes, beliefs, and practices
Religion is more than a belief in the supernatural. It's a belief in any particular view of the nature of the universe and as such zen most certainly qualifies. Zen is about reaching nirvana, which absolutely is a belief in something that is supposedly inherent in the nature of the universe. But even atheists can be considered religious. They believe there is no god so they have their belief in the nature of the universe also. They have an institutionalized belief system complete with an attending attitude.
Zen is a religion. There is no doubt about it. If you have read any of the foundation documents of Zen you would know that instantly. But even the stripped down version of zen as it is perceived in the west is a religion.