What is Allegans Contraria Non Est Audiendus?

Legal Definition
One alleging contrary or contradictory things (whose statements centradict each other) ls not to be heard. 4 Inst. 279. Applied to the statements of a witness.
-- Black's Law Dictionary
Legal Definition
Contradictory statements will not be listened to. See 28 L. R. A. 129.
-- Ballentine's Law Dictionary