The Websters Dictionary defines Wicca as the following.

Wic´ca Pronunciation: wĭk´kå
prop. n. 1. A religion derived from pre-Christian times, also called Witchcraft{4}, which practices a benevolent reverence for nature, and recognizes two deities, variously viewed as Mother & Father, Goddess & God, Female & Male, etc.; its practitioners are called Wiccans, Wiccas, or witches. Since there is no central authority to propagate dogma, the beliefs and practices of Wiccans vary significantly.

2. A practitioner of Wicca, also commonly called a Wiccan, Wicca, or witch .