There are multiple definitions - click on the translation that matches your context.

nieważność

rzeczownik

full

nullity

noun

Definitions of nullity

a marriage that is ruled to have never been in effective existence

The judge ruled their 'marriage' in Bali in 1990 was not valid either in Indonesia or under English law, and a decree of nullity was granted to Hall.

an action that has no legal validity

The Court of Appeal rejected his claim that his trial was a 'nullity because the indictment had not been officially signed'.