Dutch auction

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

• noun An auction in which an item is initially offered at a high price that is progressively lowered until a bid is made and the item sold.

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

• noun an auction where many of the same item are sold.
• noun a reverse auction that starts at a high price that is gradually reduced by the auctioneer until someone is willing to buy

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

• noun a method of selling in which the price is reduced until a buyer is found