We need to discuss how to prevent accidents.
While Viet and the others were defending themselves against the enemy, Kristen had Prince Koichi escape to Japan.
This down jacket will really protect you from the cold.
You're doing a prevention. When you prevent something, what are you really doing? You're trying to defend against something from happening. That's why this verb is a little weird and means to defend or to protect against. It can also be to prevent, too, but just make sure you're thinking of it more like you're defending something with your prevention.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: You want to defend yourself? You should probably put out that fuse (ふせ) attached to that giant bomb first then.