1. past tense and past participle of negate; made ineffective or invalid; nullified
2. past tense and past participle of negate; denied the existence or truth of something

Examples

• The new evidence negated their previous theory.
• His careless mistake negated all his hard work.
• The contract was negated by the court ruling.
• She negated his claims with solid proof.
• The benefits were negated by the high costs.
• The witness negated the defendant’s alibi.