ZIP Code. ZIP Codes are a system of postal codes used by the United States Postal Service since 1963. The term ZIP, an acronym for Zone Improvement Plan, was chosen to suggest that the mail travels more efficiently, and therefore more quickly (zipping along), when senders use the code in the postal address.
It seems to me that the OED's definition of expeditionary as a noun relates to the other sense of expedition, the sense in which expedition relates to the verb expedite. Far be it from me to dismiss Wikipedia's use of expeditionaries as incorrect. It's obvious what is meant by the word, whether or not it's in dictionaries. I would say that people who use the word are using it in such a way that it follows the pattern of revolutionary:
Define missionary: a person undertaking a mission and especially a religious mission â missionary in a sentence a person undertaking a mission and especially a religious missionâ¦ See the full definition