1 : a system of rules that explain the correct conduct and procedures to be followed in formal situations
(noncount)
The soldier’s actions constitute a breach of military protocol.
(count)
They did not follow the proper diplomatic protocols.
What is the proper protocol for declining a job offer?
2 : (count) : a plan for a scientific experiment or for medical treatment
an experimental protocol
a simplified treatment protocol
3 : (count) formal : a document that describes the details of a treaty or formal agreement between countries
the Geneva Protocol of 1925
4 : (count) computers : a set of rules used in programming computers so that they can communicate with each other
an Internet protocol