A worker who holds multiple jobs or contracts in multiple fields with multiple companies.
Portfolio workers, on the other hand, may spend a total of one week a month consulting, two weeks working part time for a major computer manufacturer, four days a month working on a book they're writing, and then another chunk of time studying. The result is a less secure but more fulfilling career.
Dawn Chipman, "A glossary of managerese; management terms," Across the Board, November, 1993
For portfolio workers, money comes in fits and starts from different sources. There may be a bit of pension, some part-time work, some fees to charge or things to sell. Portfolio people lead cash-flow lives, not salary lives.
Charles Handy, The Age of Unreason, McGraw-Hill, December 1990
The portfolio worker's series of jobs and contracts is called, not surpringly, their portfolio career. Both phrases were probably coined by the academic Charles Handy, although portfolio career is slightly older:
Seminars in recent weeks on the role of older managers, run by the outplacement firm Drake Beam Morin and by a new group, Third Age Network, have been well attended. At the latter, the Carnegie UK Trust announced the launching of a Pounds 750,000 three-year inquiry into Life, Work and Livelihood in the Third Age, a term that broadly means the years from 50 to the mid-seventies. ...
The biggest problem faced by people making a third-age switch is actually finding work. Partly this is a matter of getting used to new work patterns and making an adjustment to what Handy calls the "portfolio career" of having clients and customers, rather than jobs and employers. ''Within organisations, people are basically reacting to situations. With a portfolio career there is no in-tray, only an out-tray,'' he said at the Third Age Network conference.
Godfrey Golzen, "New age ahead for the over-fifties," The Sunday Times of London, May 20, 1990