buyback

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

• noun An act of buying something that one previously sold or owned.
• noun The repurchase of stock by the company that issued it, as to reduce holdings of a single investor or increase the value of shares by reducing their number.

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

• noun The repurchase of something previously sold, especially of stock by the company that issued it.
• noun A government purchase scheme intended to achieve a specific goal such as habitat protection or a reduction in firearm numbers.
• noun A free drink given to a patron by a bartender.

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

• noun the act of purchasing back something previously sold