A business glossary defines the language of the business, not of the database. Each entry typically includes the term, a plain definition, the person who owns it, any synonyms or abbreviations, related terms, and links to the tables, fields and reports where it is used.
It differs from a data dictionary, which documents tables and fields in technical terms. The glossary says what “new patient” means. The dictionary says which column holds it and what type of data that column contains. The two work best when they are linked.
The main purpose of a business glossary is to prevent the same word from meaning different things to different teams. In pharma, terms such as new patient, active account, net sales, covered lives and market share are each defined in more than one way inside most companies, usually for good local reasons. A glossary makes the definitions explicit, settles which one is official, and gives each an owner who decides when it changes.
A glossary that nobody maintains quickly becomes another source of confusion. Ownership, a simple change process and links from reports back to definitions keep it useful. See KPI drift.