Agony refers to extreme physical or mental suffering. It's that gut-wrenching feeling when you're going through something really tough, like a breakup or a serious injury.
The word "agony" comes from the Greek word "agonia" meaning "a struggle for victory". Nowadays we use it to describe:
1. Intense physical pain (e.g. "He was in agony after the accident")
2. Extreme mental distress (e.g. "The agony of waiting for test results")
3. A difficult struggle (e.g. "The agony of defeat")
Fun fact: In gaming slang, "agony" sometimes refers to that frustrating feeling when you keep dying in a video game.