Avoid citing Wikipedia. If you need to use information from Wikipedia, look in the "References" and the "External Links" sections for credible sources for that information. If you can't find a better source for the information and simple must use it, then include the date that you accessed it in your citation.
Template:
Title of Entry. (n. d.). In Wikipedia. Retrieved Month Day, Year from http://en.wikipedia.org/wiki/...
Example:
Utilitarianism. (n. d.). In Wikipedia. Retrieved December 1, 2013 from http://en.wikipedia.org/wiki/Utilitarianism