1. Not in accordance with the fact or reality or actuality
2. Erroneous and usually accidental
3. Arising from error; SYN. mistaken.
4. Deliberately deceptive; SYN. hollow.
5. Designed to deceive
6. Inaccurate in pitch; SYN. off-key, sour.
7. (Used especially of persons) Not dependable in devotion or affection; unfaithful SYN. untrue.
8. Of a statement, untrue. Falseness is used in proving propositions by considering the negative of the proposition to be true, then making deductions until a contradiction is reached which proves the negative to be false and the proposition to be true.

In a false or faithless manner; treacherously