(1) In common usage (and how it is used both in our book and in my Getting Published blog), a typeface/type family. (2) More properly, the full set of characters of a typeface in a specific style (indeed, in earlier times, with specific weights), e.g. Baskerville semibold italic. A key feature of the digital revolution in publishing has been the huge advances in typographical design, not least the development of Open Type fonts.
This definition is extracted (and expanded on) from the book Getting Published: A Companion for the Humanities and Social Sciences by Gerald Jackson and Marie Lenstrup. It was first referred to in the blog Getting Published in a post on issues with fonts and diacritical marks.