Hedging The practice of offsetting the price risk in an existing security by the purchase or sale of a derivative security, such as an option or futures contract.
Hidden Quantity The quantity which the broker does not wish to reveal on the Market by Order Book.
Holder The purchaser of a call or a put option.
Holding Company  A corporation that owns the securities of another company, usually with voting control.
Horizontal Merger A merger involving two or more firms in the same industry that are both at the same stage in the production cycle; that is, two or more competitors.
Hostile Takeover A takeover of a company (usually made by an open tender offer to shareholders) against the wishes of the current management and the Board of Directors by an acquiring company or raider.
House Call Notification by a brokerage house that a customer's margin account is below the minimum maintenance level. The client must provide more cash or equity, or the account will be liquidated.
Hung Up  Used to describe the position of an investor whose stocks or bonds have dropped in value below their original purchase price.
Hypothecation Pledging of securities to brokers as collateral for loans made to purchase securities or to cover short sales.