Also often called production manager, managing editor, desk editor, etc. The person who coordinates the transformation of an unedited manuscript into a printed book ready for sale. While much or all of this work is done outside the press, generally the production editor is located in-house.
The role of the production editor cannot be understated. Although the publication process looks to be a reasonably straightforward one, it involves quite a range of people undertaking about a hundred distinct tasks. Making sure that everything is done (and done at the right time) requires superb organizational skills and/or a strong set of procedures in place. The central role of the production editor in this process is crucial. Some presses are renowned within the industry for their well-oiled production machines (and others for being utterly chaotic), much of this due to the abilities or otherwise of their respective production editors.
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 calculating book length but discussed in far greater detail in another post on different editorial staff.