This paper addresses the conceptual ambiguity and unidimensionality in the understanding of robot autonomy in human-robot interaction (HRI). It proposes a comprehensive taxonomy of six distinct forms of robot autonomy: operational autonomy, intentional autonomy, shared autonomy, non-deterministic autonomy, cognitive autonomy, and physical autonomy. The taxonomy integrates interdisciplinary literature on human autonomy, including philosophy, psychology, and other fields, to provide a more nuanced and precise understanding of robot autonomy. The paper also discusses future considerations such as moral consequences, the idealization of "full" robot autonomy, and connections to agency and free will. The authors encourage HRI researchers to clarify the specific form of autonomy they are studying and to extend and critique the taxonomy to better evaluate the evolving nature and effects of autonomous robots in human society.This paper addresses the conceptual ambiguity and unidimensionality in the understanding of robot autonomy in human-robot interaction (HRI). It proposes a comprehensive taxonomy of six distinct forms of robot autonomy: operational autonomy, intentional autonomy, shared autonomy, non-deterministic autonomy, cognitive autonomy, and physical autonomy. The taxonomy integrates interdisciplinary literature on human autonomy, including philosophy, psychology, and other fields, to provide a more nuanced and precise understanding of robot autonomy. The paper also discusses future considerations such as moral consequences, the idealization of "full" robot autonomy, and connections to agency and free will. The authors encourage HRI researchers to clarify the specific form of autonomy they are studying and to extend and critique the taxonomy to better evaluate the evolving nature and effects of autonomous robots in human society.