a round robin
1. In sports, a tournament in which all participants must face everyone else in successive turns. Hyphenated if used as a modifier before a noun. Because we had an odd number of teams, we decided to make the tournament a round robin. There will be four round-robin competitions, with the winner of each one going into a final bracket on Sunday.
2. A document signed in a circle around the edges to mask the order of the signatures (so that a leader of the message cannot be identified). Employees opposing the move have decided to send a round robin to management outlining their protest.