This study explores how the climbing-centred Instagram account @cruxingincolor showcases the specialized register of mountaineers as part of its “Term Tuesdays”. The transmission of mountaineering vocabulary via Instagram represents a kind of “citizen lexicography”, with the affordances of social media platforms being utilized in creative – but also ultimately transient – ways to give attention to a highly specialized (and, on a global scale, relatively small) community and its register. Furthermore, by investigating the definitions of showcased mountaineering expressions and how they are presented on @cruxingincolor, the study underscores that mobility is a concept inherent to the sport to the extent of being an important part of many of the sport’s key expressions. The results reveal that, while the investigated entries typically focus on physical mobility, some also pertain to aspects such as the impact of mountaineering on the environment or its role in upcoming events. Thus, overall, the contribution shows that the citizen lexicography approach evident on @cruxingincolor is affected by and represents multiple layers of transient mobility.