1. 印象;感想
    Your impression of a person or thing is what you think they are like, usually after having seen or heard them. Your impression of a situation is what you think is going on.

    e.g. What were your first impressions of college?...
           你对大学的第一印象是什么？
    e.g. My impression is that they are totally out of control...
           我的感觉是它们完全失去了控制。

2. (通常有悖事实的)感觉,假象
    If someone gives you a particular impression, they cause you to believe that something is the case, often when it is not.

    e.g. I don't want to give the impression that I'm running away from the charges...
           我不想给人一种我在逃避指控的感觉。
    e.g. He cleverly inserted mirrors above the window to create an impression of space.
           他巧妙地在窗子上面镶嵌了几面镜子，以营造一种空间感。

3. (通常指对名人的)滑稽模仿
    An impression is an amusing imitation of someone's behaviour or way of talking, usually someone well-known.

impression

    e.g. He did impressions of Sean Connery and James Mason.
           他对肖恩·康纳利和詹姆斯·梅森进行了滑稽模仿。

4. 压痕;印痕;印记
    An impression of an object is a mark or outline that it has left after being pressed hard onto a surface.

impression

    e.g. ...the world's oldest fossil impressions of plant life.
           世界上最古老的植物化石印痕

5. 产生影响;起作用
    If someone or something makes an impression, they have a strong effect on people or a situation.

    e.g. He has told me his plans and he's made a good impression on me...
           他告诉了我他的计划,给我留下了一个好印象。
    e.g. The aid coming in has made no impression on the horrific death rates.
           逐渐到达的救援对可怕的死亡率并没有起到什么作用。

6. (误)认为;(错)以为
    If you are under the impression that something is the case, you believe that it is the case, usually when it is not actually the case.

    e.g. He had apparently been under the impression that a military coup was in progress.
           他显然以为一场军事政变正在酝酿中。