The United Nations’ Intergovernmental Panel on Climate Change (IPCC) and other institutions communicate about climate change to diverse audiences without a background in climate science, including the general public. The effectiveness of these communications depends in part on how well the presented terminology is understood. In qualitative interviews, we examined how US residents interpreted key terms drawn from IPCC reports, including tipping point, unprecedented transition, carbon neutral, carbon dioxide removal, adaptation, mitigation, sustainable development, and abrupt change. We recruited twenty participants with diverse views on climate change from a nationally representative sample. We identified common themes and misunderstandings. Overall, 88% of the themes arose by the tenth interview, and no new themes arose after the seventeenth interview. Mitigation, carbon neutral, and unprecedented transition were perceived as the most difficult to understand. Adaptation and abrupt change were perceived as the easiest to understand. However, even if a term appeared to be understood, participants were not always clear about how it applied to climate change. Participants tended to draw on their mental models of non-climate contexts where terms had different meanings. Reading the terms in the context of sentences taken from communication materials was not always helpful due to the use of complex language. Based on participants’ interpretations and the science communication literature, we provide suggestions for communicating about each term. Generally, recommendations are to simplify wording, make links to climate change explicit, and describe underlying processes. Our findings are relevant to climate change communications by the IPCC and other institutions.