Cite your source dictionary this way in APA style: Pompion. (1993). In The new Oxford shorter English dictionary (11th ed., Vol. 2). Oxford: Oxford University Press.
Cite your source dictionary this way in MLA style: "Pompion." Entry 1. The New Oxford Shorter English Dictionary. 1993. Print.
Cite your source dictionary this way in Chicago or Turabian style if the dictionary is not well known: Dictionary of Weird Words, rev. ed. (Purple, OK: Domino Editions, 1993), s.v. "pismire."
Do not cite your source dictionary in Chicago or Turabian style if the dictionary is well known.