negate

Verb

• make ineffective by counterbalancing the effect of
  • Her optimism neutralizes his gloom
    
  • This action will negate the effect of my efforts
    

• prove negative; show to be false

• deny the truth of

• be in contradiction with

Related words

• Synonyms: 
  neutralize , neutralise , nullify , contradict , contravene , belie
• Antonyms: 
  confirm , corroborate , sustain , substantiate , support , affirm