Although tourism destination image (TDI) has been extensively studied, the nature and scope of TDI remain vague. This study aims to address this conceptual problem from a modernist perspective. Forty-five representative TDI definitions are analyzed, and a new definition is proposed by adopting a "seven-step" procedure derived from definition theory in logic studies. Results show that (1) currently TDI is defined mainly as the mental/total impressions/perceptions held by tourists pertaining to a destination, (2) such definitions are quasi-theoretical in type and created by roughly following the connotative definition technique, (3) the quality of these definitions is generally low, and (4) the new definition proposed in this study better captures the essence of TDI and considerably reduces TDI’s internal and external vagueness. In defining a key tourism concept, this study has notable implications for advancing TDI research and defining tourism concepts more rigorously.