nullify
['nʌl.ɪ.faɪ] verb transitive formal
■to make a legal agreement or decision have no legal force 使（协议或决议）失去法律效力•The state death penalty law was nullified in 1977.该州于1977年废除了死刑。 ■to cause something to have no value or effect 使无价值；使无效•All my hard work was nullified when I lost my notes.由于遗失了笔记，我所有的辛苦心血都化为乌有了。 |