broker

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that acts as an agent for others, as in negotiating contracts, purchases, or sales in return for a fee or commission.
• noun A stockbroker.
• noun A power broker.
• transitive verb To arrange or manage as a broker.

from The Century Dictionary.

• noun A middleman or agent who, for a commission or rate per cent. on the value of the transaction, negotiates for others the purchase or sale of stocks, bonds, commodities, or property of any kind, or who attends to the doing of something for another.
• noun One who lends money on pledges, or lets out articles for hire; a pawnbroker, or a lender of goods.
• noun A pimp or procurer; a pander.
• noun One who has ‘gone broke’; a ‘dead broke,’ ruined, or bankrupt man.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who transacts business for another; an agent.
• noun (Law) An agent employed to effect bargains and contracts, as a middleman or negotiator, between other persons, for a compensation commonly called brokerage. He takes no possession, as broker, of the subject matter of the negotiation. He generally contracts in the names of those who employ him, and not in his own.
• noun A dealer in money, notes, bills of exchange, etc.
• noun engraving A dealer in secondhand goods.
• noun obsolete A pimp or procurer.
• noun one who buys and sells notes and bills of exchange.
• noun [U.S.] an operator in stocks (not a member of the Stock Exchange) who executes orders by running from office to office, or by transactions on the street.
• noun one who buys and sells uncurrent money, and deals in exchanges relating to money.
• noun one who is agent in procuring insurance on vessels, or against fire.
• noun See Pawnbroker.
• noun one who buys and sells lands, and negotiates loans, etc., upon mortgage.
• noun one who acts as agent in buying and selling ships, procuring freight, etc.
• noun See Stockbroker.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A mediator between a buyer and seller.
• noun computing An agent involved in the exchange of messages or transactions.
• verb To act as a broker; to mediate in a sale or transaction.
• adjective comparative form of broke: more broke

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb act as a broker
• noun a businessman who buys or sells for another in exchange for a commission