When you cite a dictionary entry on an APA reference list, you will not have an author byline, so the entry's title goes first. Then include the date of the entry in parentheses, or "n.d." if there is no date given. If the dictionary is online, include the Web address. For print editions, include the edition, location and name of the publisher.
Example of an online dictionary entry:
Espresso. (n.d.) In Merriam-Webster's online dictionary (italicized). Retrieved from http://www.merriam-webster.com/dictionary/espresso.
Example of a print dictionary entry:
Existentialism. Merriam-Webster's collegiate dictionary (italicized) (11th ed.). (2005). Springfield, MA: Merriam-Webster.
Use the dictionary entry's title in parentheses. The entry should be in quotation marks, since it is not a full work. Other punctuation marks go outside of the parentheses.
("Espresso," n.d.) ("Existentialism," 2005)