A military officer, usually a skilled technician or a helicopter pilot, intermediate in rank between a noncommissioned officer and a commissioned officer, having authority by virtue of a warrant.
My annual evaluation reports always included the phrase "Technical and tactical expert..." In modern parlance, because Warrant Officers have now become commissioned and are branched, we refer to the "other" officers as RLO's or Real Life Officers. The biggest difference is that Warrants are on a technical track, doing the same thing at more complex levels for an entire career, while RLO's are on a command track, hoping to one day be Chief of Staff. The only services which still employ Warrants are the Army and Marine Corps. On a side note, there are some Warrants who inadvertantly find themselves in command positions, some by design, and some because the higher RLO can't find a subordinate RLO that he trusts enough to get the job done.
I found a sheet that kind of defines the attitudes of Warrant Officers.
It's good to be the king.