Citing an online dictionary entry
Note: Popular dictionaries should be referenced in the notes only, but lesser-known dictionaries can be included in the bibliography. See sections 14.247 and 14.248 of the Chicago Manual of Style for additional information.
Dictionary title, s.v. “Definition word,” by First name Last name (if applicable), accessed Month Date, Year, URL.
Note: Here is how you would cite the entry for “food baby” from an online dictionary accessed October 22, 2013 in your notes:
Oxford Dictionaries, s.v. “food baby,” accessed October 22, 2013, http://www.oxforddictionaries.com/definition/english/food-baby.