Dealer
Definition: An entity that stands ready and willing to buy a security for its own account (at its bid price) or sell from its own account (at its ask price). Individual or firm acting as a principal in a securities transaction. Principals are market makers in securities, and thus trade for their own account and risk. Antithesis of broker. See: Agency.

Dealer
Definition: An individual or firm that acts as a market maker in an instrument such as a security or foreign currency.