protocol // n 1 [U] system of rules governing formal occasions, eg meetings between governments, diplomats, etc; official etiquette: The organizer was familiar with the protocol of royal visits. * The delegates have to be seated according to protocol. * a breach of protocol. 2 [C] (formal) first or original draft of a diplomatic agreement, especially of the agreed terms for a treaty. 3 [C] a standard way of communicating across a network; a protocol is the "language" of the network; a method by which two dissimilar systems can communicate. TCP is a protocol which runs over a network.