One who transacts business for another; an agent; a
   substitute; especially, a mercantile agent who buys and sells goods and
   transacts business for others in commission; a commission merchant or
   consignee. He may be a home factor or a foreign factor. He may buy and
   sell in his own name, and he is intrusted with the possession and
   control of the goods; and in these respects he differs from a broker.