The term Pagan originates from the latin word Paganus. It meant 'country dweller' and was a derogatory term used by early christians. It basically meant 'Hick'.
In neo-paganisms, we hope the word has taken on a more positive meaning. It refers to nature religions, old and new, (wicca is a very young religion). A strong theme of nature religions, is a belief in animism, that is, that every living thing has a spirit or a soul. Paganism reveres the divine in all things.
There are monotheist nature religions, like Dianic Wicca. Some focus on a single Life Force of no specific gender. It is more the reverence for the natural world that we enjoy, rather than the number of deities acknowledged, that defines pagan religions from others.