Definition of "nullify" []

• To make null; invalidate. (verb-transitive)
• To counteract the force or effectiveness of. (verb-transitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Curb asks a judge to force McGraw to turn in new material for a fifth album, bar him from signing with another label and nullify a 2001 agreement that eliminated a sixth record from McGraw's contract."
• "At the tea parties, in the attempts by states including Virginia to "nullify" health care, and in parts of the originalism jurisprudence of conservatives on the Roberts Court, there is strong sense of nostalgia for the unamended Constitution and the ideas of our founding, even when those ideas have been repudiated by subsequent constitutional history and overruled or limited by constitutional Amendments."
• "But while such efforts serve as healthy political protest, federal laws that are constitutional are supreme under the 10th Amendment, and states can't "nullify" a Congressional action."