contractor

To look at it another way, someone who is so technically skilled that to place them in just one office would be a waste to the world. Also they are generally so smart in skill areas where there is a shortage that most businesses cannot afford to keep them on for long periods of time and thus hire them for three or six months at the most, or until someone in the Finance Department realises just how much is being paid for one guy.

I like the second definition better but then I am a contractor so maybe my viewpoint is skewed.

Con*tract"or (?), n. [L.]

One who contracts; one of the parties to a bargain; one who covenants to do anything for another; specifically, one who contracts to perform work on a rather large scale, at a certain price or rate, as in building houses or making a railroad.

© Webster 1913.