a code of conduct, etiquette, and procedure, esp for official or ceremonial occasions
You wonder whether the heat and the heavy robes will all be too much. What is the protocol for removing a collapsed Knight of the Garter? — Jeremy Paxman
an original draft of a diplomatic document, e.g. a treaty
an amendment or annexe to a treaty
a signed record of agreement made at a diplomatic conference, international negotiations, etc
in computing, a set of rules relating to the form in which data must be presented, e.g. for transmission between computers
the plan or a record of a scientific experiment or medical treatment
[early French prothocole via Latin from late Greek prōtokollon first part of a papyrus roll bearing details of manufacture or contents, from proto- + Greek kollan to glue together, from kolla glue]