office wife n. a female secretary or executive assistant; a female worker devoted to a powerful man to whom she is not married, especially a man in a hierarchically superior position; a female coworker who is a friend. Also office spouse, work wife. Editorial Note: The term office husband or uses of office spouse in which the “spouse” is male are less common. (source: Double-Tongued Dictionary)
Among people I know, the term “office husband” is used just as frequently as “office wife” and, like the roles of most husbands and wives in the 21st century, is complex, and unrelated to specific hierarchical positions. It’s a person of the opposite sex (or the same sex, if you are gay) with whom you have a close daily interdependent relationship, except that it only takes place in the confines of the office and does not involve sex.