reversal

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

• noun The act or an instance of reversing.
• noun The state of being reversed.
• noun A usually adverse change in fortune.
• noun Law The act or an instance of changing or setting aside a lower court's decision by a higher court.
• noun Sports A maneuver in wrestling in which a competitor being controlled by the opponent suddenly reverses the situation and gains control.

from The Century Dictionary.

• noun In international law: A promise by a sovereign power that a certain order, or certain conditions, promulgated or established, will be observed, notwithstanding changes that may occur to cause deviation therefrom. For instance, when France recognized Russia as an imperial government, a reversal was required that Russia would not cause any derogation from the rank which France had held toward her.
• noun A declaration by a sovereign that by a given act he means no prejudice to another power.
• noun In electricity, the process of changing the direction of the current in a circuit. In telegraphy the term is applied to the sending of signals over the line by means of rapidly reversed or alternating currents.
• noun The act of reversing, or of altering a position, direction, action, condition, or state to its opposite or contrary; also, the state of being reversed.
• noun In physics, specifically, the changing of a bright line in a spectrum, produced by an incandescent vapor, into a dark line (by absorption), and the reverse.
• noun The act of repealing, revoking, or annulling; a change or overthrowing: as, the reversal of a judgment, which amounts to an official declaration that it is erroneous and rendered void or terminated; the reversal of an attainder or of an outlawry.
• noun In biology, reversion.
• Causing, intending, or implying reverse action; reversing.

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

• noun The act of reversing; the causing to move or face in an opposite direction, or to stand or lie in an inverted position
• noun A change or overthrowing
• adjective obsolete Intended to reverse; implying reversal.

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

• noun The state of being reversed.
• noun An instance of reversing.
• noun A change in fortune; a change from being successful to having problems.

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

• noun an unfortunate happening that hinders or impedes; something that is thwarting or frustrating
• noun a judgment by a higher court that the judgment of a lower court was incorrect and should be set aside
• noun turning in the opposite direction
• noun a change from one state to the opposite state
• noun turning in an opposite direction or position
• noun a decision to reverse an earlier decision
• noun the act of reversing the order or place of
• noun a major change in attitude or principle or point of view