1. 加农炮;大炮
    A cannon is a large gun, usually on wheels, which used to be used in battles.

2. (尤指机载的)自动机关炮
    A cannon is a heavy automatic gun, especially one that is fired from an aircraft.

3. 碰撞；猛撞
    If one person or thing cannons into another, they bump into them with great force.

    e.g. One of the reporters cannoned into Arnold...
           一个记者和阿诺德撞了个满怀。
    e.g. The ball cannoned off the back of a Spartak defender and into the net.
           球打在斯巴达克队一名防守队员的背上后反弹入网。

4. 为所欲为的人;冒失鬼
    If someone is a loose cannon, they do whatever they want and nobody can predict what they are going to do.

    e.g. Max is a loose cannon politically.
           马克斯在政治上我行我素。