Definition of "nullification"

The act of nullifying; a rendering void and of no effect, or no legal effect.  examples

The nullification crisis in U.S. history, confrontation between the state of South Carolina and the federal government in 1832–33 over the former's attempt to declare null and void within the state the federal Tariffs of 1828 and 1832.  examples

(neologism) Surgical removal of genitals (and sometimes nipples) as a form of body modification; a person who has undergone this surgery is a nullo.