1) Debasement 2) Nullification 3) Override 4) Rendering null 
• (n.) The act of vitiating, or the state of being vitiated; depravation; corruption; invalidation; as, the vitiation of the blood; the vitiation of a contract.
Vi`ti·a'tion noun [ Latin vitiatio .] The act of vitiating, or the state of being vitiated; depravation; corruption; invalidation; as, the vitiation of the blood; the vitiation of a contract. « The vitiation that breeds evil acts.» G. Eliot. 
Type: Term Pronunciation: vish-ē-ā′shŭn Definitions: 1. A change that impairs use or reduces efficiency.
[n] - nullification by the destruction of the legal force
vitiation 1. Injury, contamination, impairment of use or efficiency. 2. A change in a process that impairs utility or reduces efficiency. 3. Nullification by the destruction of a legal force; rendering something null: 'The court made a vitiation of the contract.' 4. The act of vitiating, or the state of being vitiated; deprivation; corruption; i...
noun nullification by the destruction of the legal force; rendering null; `the vitiation of the contract`