The subject of this book is inter-, cross- and multidisciplinary learning and teaching. Interdisciplinary learning and teaching is a collaborative, multiple-field-of-study way of engaging with all of the knowledge relevant to a subject or topic. As Kenyon, citing Klaassen (2018), explains in Chapter 10, interdisciplinary pedagogy combines “the approaches of two different disciplines … to produce an understanding of a problem and possibly a solution to a problem”. Cross-disciplinary and multidisciplinary are variations of this pedagogy: the former borrows or touches across disciplines while the latter amalgamates different disciplines. We can use these as working definitions, certainly, but what do they really mean? And does everyone use these terms in the same way? Klein (1990, p. 11) suggests that “interdisciplinarity is a concept of wide appeal [but] is also one of wide confusion”. This is our experience too. In what follows we offer readers an introduction to our struggle with definitions and the world of possibilities that confusion opened for us when encouraging pedagogical research into (originally, just) interdisciplinary learning and teaching. Our search for what cross-, inter- and multidisciplinary learning and teaching means, and the impact it has on academia and the real world, was both challenging and rewarding.