Person who's job it is to determine a fair price of a certain asset and to help buyers and sellers exchange that over-the-counter outside the market.
A trader or institution that plays a leading role in a market by being prepared to quote a two way price (Bid and Ask) on request - or constantly in the case of some screen based markets - during normal market hours.
(1) A member of an options exchange who trades for his own account and risk. He is charged with the responsibility of trading in such a manner as to add to the maintenance of a fair, orderly and competitive market. He may not act as agent. (2) A firm actively making bids and offers in the OTC market.