How do I cite a dictionary entry?
Rules #27-30 (p.204-205) all apply to reference materials. These are in Section 7.02 for Books, Reference Books, and Book Chapters. The examples vary depending on whether the reference book is print or online-based, so choose the rule according to the source you are using.
All information and page number references are based on the 6th edition of the Publication Manual of the American Psychological Association (2009/10).