During conversation, partners develop representations of jointly known information--the common ground--and use this knowledge to guide subsequent linguistic exchanges. Extensive research on 2-party conversation has offered key insights into this process, in particular, its partner-specificity: Common ground that is shared with 1 partner is not always assumed to be shared with other partners. Conversation often involves multiple pairs of individuals who differ in common ground. Yet, little is known about common ground processes in multi-party conversation. Here, we take a 1st step toward understanding this problem by examining situations in which simple dyadic representations of common ground might cause difficulty--situations in which dialogue partners develop shared labels (entrained terms), and then a 3rd (naïve) party joins the conversation. Experiment 1 examined unscripted, task-based conversation in which 2 partners entrained on terms. At test, speakers referenced game-pieces in a dialogue with their partner, or in a 3-party conversation including a new, naïve listener. Speakers were sensitive to the 3rd party, using longer, disfluent expressions when additionally addressing the new partner. By contrast, analysis of listener eye-fixations did not suggest sensitivity. Experiment 2 provided a stronger test of sensitivity and revealed that listeners do cancel expectations for terms that had been entrained before when a 3rd, naïve party joins the conversation. These findings shed light on the mechanisms underlying common ground, showing that rather than a unitary construct, common ground is flexibly adapted to the needs of a naïve 3rd party.