extortion

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

• noun Illegal use of one's official position or powers to obtain property, funds, or patronage.
• noun The act or an instance of extorting something, as by psychological pressure.
• noun An excessive or exorbitant charge.

from The Century Dictionary.

• noun The act of extorting; the act or practice of wresting anything from a person by force, duress, menace, authority, or any undue exercise of power; oppressive or illegal exaction, as of excessive price, rent, or interest.
• noun In law, strictly, the crime of obtaining money or other property, or service, from another under color of public office, when none is due, or not so much is due, or before it is due. In some of the United States, however, a wider meaning is given to the word by statute.
• noun That which is extorted; a gross overcharge: as, the price you paid was an extortion.

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

• noun The act of extorting; the act or practice of wresting anything from a person by force, by threats, or by any undue exercise of power; undue exaction; overcharge.
• noun (Law) The offense committed by an officer who corruptly claims and takes, as his fee, money, or other thing of value, that is not due, or more than is due, or before it is due.
• noun That which is extorted or exacted by force.

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

• noun The practice of extorting money or other property by the use of force or threats.

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

• noun an exorbitant charge
• noun unjust exaction (as by the misuse of authority)
• noun the felonious act of extorting money (as by threats of violence)