This short article presents a new communication abstraction denoted Mutual Broadcast (in short MBroadcast). It provides each pair of processes with the following property (called mutual ordering): for any pair of processes p and p′, if p broadcasts a message m and p′ broadcasts a message m′, it is not possible for p to deliver first (its message) m and then m′ while p′ delivers first (its message) m′ and then m. The computability power of this broadcast abstraction is the same as the one of an atomic read/write register. Interestingly, it constitutes the first characterization of RW registers in terms of (binary) message patterns.