double bind

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

• noun A psychological impasse created when a person perceives that someone in a position of power is making contradictory demands, so that no response is appropriate.
• noun A situation in which a person must choose between equally unsatisfactory alternatives.

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

• noun A dilemma in which someone receives contradictory instructions and cannot act on either.

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

• noun (psychology) an unresolvable dilemma; situation in which a person receives contradictory messages from a person who is very powerful