contradiction : Idioms & Phrases

• etc. See under Bitter, Contradiction, etc.

Webster 1913

• noun (logic) a statement that is necessarily false
  contradiction.
  
  • the statement `he is brave and he is not brave' is a contradiction

WordNet

• (Logic), the axiom or law of thought that a thing cannot be and not be at the same time, or a thing must either be or not be, or the same attribute can not at the same time be affirmed and and denied of the same subject. It develops itself in three specific forms which have been called the "Three Logical Axioms." First. "A is A." Second, "A is not Not-A" Third, "Everything is either A or Not-A."

Webster 1913

• noun contradicting yourself
  

WordNet

Self`-con`tra*dic"tion noun

Definitions

1. The act of contradicting one's self or itself; repugnancy in conceptions or in terms; a proposition consisting of two members, one of which contradicts the other; as, to be and not to be at the same time is a self-contradiction.

Webster 1913