Noun and する verb
もくさつ
警察はその地域では多くの犯罪を黙殺しています。
The police ignore most of the crime in this area.
Shut up and kill your talking or I'll kill it for you. I'm not listening to this. I'm ignoring it.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.