In interdisciplinary investigations into the relationships between pornography and its audiences, the issue of how to define the object of study is more complex than in studies situated within a single discipline. A Delphi panel of 38 leading pornography researchers from a wide range of disciplines was asked about various topics, including the definition of pornography. Qualitative and quantitative analyses of two rounds of survey responses suggested two different and—at first sight—incompatible definitions operating. This technical report suggests that we should encourage researchers to choose which definition they want to use in a self-reflective way depending on the needs of the project, so long as they make it explicit and justify their decision. In this technical report, we focus on definitions of pornography, paying particular attention to the question of whether it is possible to reach consensus on a definition across disciplines. The rise of smartphones, allowing easy private access to sexually explicit material, especially for young people, has made these issues particularly pressing for many researchers.