1. 露齿而笑；咧嘴大笑
    When you grin, you smile broadly.

grin

    e.g. He grins, delighted at the memory...
           想到往事，他开心地咧嘴笑了起来。
    e.g. Sarah tried several times to catch Philip's eye, but he just grinned at her.
           萨拉几次想引起菲利普的注意，但是他只是冲她咧嘴笑了笑。

2. 露齿的笑；咧嘴的笑
    A grin is a broad smile.

    e.g. She came out of his office with a big grin on her face...
           她笑容满面地走出他的办公室。
    e.g. Bobby looked at her with a sheepish grin.
           博比望着她腼腆地咧嘴一笑。

3. 苦笑着忍受；默默承受
    If you grin and bear it, you accept a difficult or unpleasant situation without complaining because you know there is nothing you can do to make things better.

    e.g. They cannot stand the sight of each other, but they will just have to grin and bear it.
           他们连看对方一眼都不愿意，但是也只得默默忍受。