This article presents a working definition of digital comics for the specific context of the British Library. It explores formal and sociocultural characteristics of digital comics as well as the sociocultural issues surrounding comics collections at national libraries. The article argues for the value of flexible working definitions over formal definitions, and explores the problematic issue of definitional authority at a national institution such as the British Library. The article defines what distinguishes a digital comic from a print comic, and explores visual, functional and sociocultural features of digital comics before presenting a flexible, composite working definition of a digital comic. This definition is presented in the spirit of an instrumental case study with the aim of helping to inform other context-specific working definitions of digital comics.