Jobbing pirate (more commonly jobber) is a temporary position in a crew. Jobbing pirates apply for a position on a ship (usually one that is pillaging, although sometimes ships are trading and compensate jobbers for help moving commodities) via the Notice Board.
At the end of a pillage, crew officers or above will often invite jobbing pirates to become permanent members of the crew. Crews do almost all of their recruiting in this way, as only players who are first jobbing pirates can permanently join a crew.
Depending on a crew's booty shares, jobbing pirates can sometimes be given a smaller share of the booty than higher ranks. Exception: Crews that use the Jobber's Delight booty share give slightly more to jobbing pirates than to any of other ranks.