How can we understand each other during communicative inter- actions? An influential suggestion holds that communicators are primed by each other’s behaviors, with associative mechanisms au- tomatically coordinating the production of communicative signals and the comprehension of their meanings. An alternative sugges- tion posits that mutual understanding requires shared conceptuali- zations of a signal’s use, i.e., “conceptual pacts” that are abstracted away from specific experiences. Both accounts predict coherent neu- ral dynamics across communicators, aligned either to the occurrence of a signal or to the dynamics of conceptual pacts. Using coherence spectral-density analysis of cerebral activity simultaneously mea- sured in pairs of communicators, this study shows that establishing mutual understanding of novel signals synchronizes cerebral dy- namics across communicators’ right temporal lobes. This interper- sonal cerebral coherence occurred only within pairs with a shared communicative history, and at temporal scales independent from signals’ occurrences. These findings favor the notion that meaning emerges from shared conceptualizations of a signal’s use.