Although faculty agree that critical thinking is an important learning outcome for college courses, experts disagree on how to define and conceptualize critical thinking. Some researchers see it as a general skill, similar to reading or mathematics. Others see it as highly specific to each academic discipline, with critical thinking in one discipline being qualitatively different than critical thinking in another discipline. However, researchers to date have not yet tried to conceptualize how critical thinking might systematically vary across disciplines. The purpose of this study was to gather definitions of critical thinking from faculty in a range of disciplines and compare these domain-specific definitions to each other. Across disciplines, faculty defined critical thinking as applying knowledge to new situations, considering different viewpoints, evaluating options and evidence, and having a critical thinking disposition. The article concludes with suggestions for fostering critical thinking skills in general education courses.