1. 额；额头
    Your brow is your forehead.

    e.g. He wiped his brow with the back of his hand...
           他用手背擦了擦前额。
    e.g. She wrinkled her brow inquisitively.
           她好奇地皱起了眉头。

2. to knit your brow -> see knit

3. 眉；眉毛
    Your brows are your eyebrows.

    e.g. He had thick brown hair and shaggy brows.
           他一头浓密的棕色头发，眉毛乱糟糟的。

4. 山脊；坡顶
    The brow of a hill is the top part of it.

    e.g. He was on the look-out just below the brow of the hill.
           他就在山脊下负责警戒。