This paper examines the contribution of Horae Subsecivae to Joseph Wright's (1855–1930) English Dialect Dictionary (1896–1905) (EDD). Horae Subsecivae (‘spare hours’) is an obscure manuscript glossary that was possibly compiled by Robert Wight of Wotton-under-Edge in c.1777–78, and is now preserved amongst Wright's papers at the Bodleian Library as Bodl. MS Eng. lang. d. 66. Even though it has received little scholarly attention, Horae Subsecivae has a substantial dialect element, with a large number of words cited from Devonshire, Dorset, Cornwall, Gloucestershire, Somerset, Wiltshire and Worcestershire. The manuscript went largely unnoticed by 18th- and 19th-century collections, and remains virtually unknown today perhaps owing to its extensive use of Latin, but it drew the attention of Joseph Wright, who employed it frequently to represent some western dialects. Drawing on the electronic version of the EDD (EDD Online; Markus, 2019a), the paper is situated within forensic dictionary analysis (Coleman & Ogilvie, 2009), which ‘uses evidence-based methodologies to interrogate the dictionaries themselves about decision-making processes involved in their compilation’ (1). In this framework, I combine archival material with quantitative and qualitative approaches to the data retrieved from EDD Online in order to ascertain the proportion of words that are cited from the manuscript, and to assess the treatment they are given. Attention is paid to their function in the context of the dictionary, labels, the western dialects about which the manuscript provides more extensive information, as well as the entries in which it is cited as the only source for words, ascriptions and senses. This paper highlights the outstanding contribution of Horae Subsecivae to the EDD, while stressing that it notably improves our knowledge of lexical variation in the dialects of the South West and the lower West Midlands. They can only benefit from further inspection as they ‘are neither as easily found nor as well researched as those of the north’ (Melchers, 2010: 82).