bad faith

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

• noun The malicious intention to be dishonest or to violate the law, as in negotiations over a contract.

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

• noun law A malicious motive by a party in a lawsuit. This has an effect on the ability to maintain causes of action and obtain legal remedies.
• noun law Intent to deceive or mislead another to gain some advantage; dishonesty or fraud in a transaction (such as knowingly misrepresenting the quality of something that is being bought or sold).
• noun philosophy The existentialist concept of denying one's total freedom of will.