This book is a critiqued collection of over 200 terms regularly used to name the urban void, from terrain vague to buffer zone. As the landscape architect James Corner has pointed out, a void cannot be labeled because “to name it is to claim it in some way.” By listing existing terms, A Glossary of Urban Voids attempts to name the unnamable, to define that which should have no precise definition. It records terms, names, and labels used to designate leftover spaces, resulting from processes of urban abandonment, that originate from some kind of obsolescence or loss. In addition to their obvious consequences, these processes of abandonment open up space, liberating it from existing ideological frameworks (financial, capital, cultural …), allowing divergent spatialities to emerge, and ultimately offering opportunities to imagine and conceptualize an alternative type of public space. Using the glossary as an intellectual tool, this book presents the most relevant questions on the issue of the urban void and its potential role as public space.