The importance of, and interest in, sustainability in management education has increased significantly over the past three decades. However, the definition of sustainability remains complex and elusive, thus creating significant issues for sustainability instruction, assignment design, and student learning. We reviewed definitions and use of sustainability and corporate social responsibility (CSR) nomenclature from academics, corporations, and business and society course textbooks. The evidence is clear that sustainability and CSR are commonly and frequently used interchangeably not only in academic research and the classroom but also by textbook authors and business reports. Using a sustainability assignment gone wrong, we present data and analysis showing that this lack of definitional clarity and intermingling of the concepts of sustainability and CSR led to problems with student learning and outcomes from the assignment. Student work was heavily influenced by corporate terminology, which superseded textbook, nomenclature, and classroom instruction. We call for future research to delve into the issue of clarifying the definitional complexity and conflation.