Found in the book [[Fifty Years of Dungeons and Dragons]]

“The fictional events of play in a role-playing game are dependent on the consensus of the players involved in order to be accepted as having occurred. All formal and informal rules, procedures, discussion, interactions and activities which form this consensus comprise the full system used in play”

This basically means that all players must agree, through rules, discussion, or other forms of decision making that events in the game are progressing and occur specifically in one way. The rules and procedures which allow a group of people to come to that consensus is what Emily Care Boss, Vincent Baker, and Meguey Baker claim roleplaying is - a structured conversation in which we manage our groups consent to fictional events.

Role-playing is a conversation with rules and structures, which we use to agree upon imaginary events that fictionally occur.