A standardized form of communication that allows EDI exchange (or other data exchange) between multiple computers.

Merriam-Webster Online Dictionary
protocol (noun)
1.
an original draft, minute, or record of a document or transaction
2.
a) a preliminary memorandum often formulated and signed by negotiators as a basis for a final convention or treaty - diplomatic
b) the records or minutes of a diplomatic conference or congress that show officially the agreements arrived at by the negotiators
3.
a) a code prescribing strict adherence to correct and (as in diplomatic exchange and in the military services) - etiquette precedence a breach of protocol
b) a set of conventions governing the treatment and especially the formatting of data in an electronic communications system - network protocols
c) - convention
4.
a detailed plan of a scientific or medical experiment, treatment, or procedure