Downfall, Ruin, Destruction
noun, verbal noun
Destroy to death. If you are destroyed to this point, this will be your downfall and ruin.
めつぼう
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
もしその超巨大火山が噴火をすれば、我々は滅亡を免れないだろう。
If the super volcano erupted, we would not be able to escape destruction.