nullify
verb [ T ] uk/ˈnʌl.ɪ.faɪ/ us/ˈnʌl.ə.faɪ/
formal使（协议或决议）失去法律效力
to make a legal agreement or decision have no legal force
The state death penalty law was nullified in 1977. 该州于1977年废除了死刑。
使无价值;使无效
to cause something to have no value or effect
All my hard work was nullified when I lost my notes. 由于把笔记弄丢了，我所有的辛苦劳动都化为乌有。