We examined lexical choice and variability in referring expressions during direction-giving to pedestrians. A stationary partner (the Giver) directed a mobile partner by telephone (the Follower) to walk about 1.8 miles, to 18 destinations on a medium-sized campus. Followers returned to the lab and partners were tested individually on their spatial ability and memory for the destinations; then they participated in 6 rounds of a referential communication task to repeatedly match duplicate copies of pictures of the destinations. Results include significant rates of lexical entrainment and evidence for partner-specific conceptual pacts. Joint navigation efficiency was affected by direction-givers’ (but not followers’) spatial ability. The Walking Around Corpus, an experimentally parameterized collection of spontaneous spoken dialogues produced by 36 pairs of people communicating by mobile telephone, provides a testbed for lexical entrainment “in the wild” as well as a resource for pedestrian navigation applications; it is available to the research community.