Our paper presents a macro- and micro-structural overview of medical terminology in Bailey’s An Universal Etymological English Dictionary (1721), a general-purpose dictionary that served as a model for other eighteenth-century lexicographical works including Samuel Johnson’s celebrated Dictionary of the English Language (1755). Accordingly, we first offer some key notes on Bailey’s dictionary for contextualisation purposes. Then, we address his own definition of medicine as a reference point that could help decide what terms and expressions may be considered medical in the absence of any other information or clue in a particular dictionary entry. Finally, we examine Bailey’s strategies to single out medical terminology, the overall structure of individual medical entries and the most common methods of definition deployed in the A-Z wordlist.