This book is a critiqued collection of over 200 terms regularly used to name the urban void, from the terrain vague to the 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 is an attempt 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. Besides obvious consequences, these processes of abandonment open up the space, liberating it from existing ideological frameworks (such as financial, capital, or cultural frameworks), allowing for divergent spatialities to emerge, and ultimately offering opportunities for the imagination and conceptualization of an alternative type of public space. Using the glossary as a theoretical tool, this book presents the most relevant questions on the issue of the urban void and its potential role as public space.