1. 反馈;反应
    If you get feedback on your work or progress, someone tells you how well or badly you are doing, and how you could improve. If you get good feedback you have worked or performed well.

    e.g. Continue to ask for feedback on your work...
           继续征求对你的工作的反馈意见。
    e.g. I was getting great feedback from my boss.
           老板对我的评价很高。

2. (电器设备的)反馈噪音
    Feedback is the unpleasant high-pitched sound produced by a piece of electrical equipment when part of the signal that comes out goes back into it.