1. 咯咯地笑；傻笑
    If someone giggles, they laugh in a childlike way, because they are amused, nervous, or embarrassed.

    e.g. Both girls began to giggle...
           两个女孩都咯咯地笑了起来。
    e.g. 'I beg your pardon?' she giggled.
           “您可以重复一遍吗？”她咯咯地笑着说。

2. 傻笑
    If you say that someone has the giggles, you mean they cannot stop giggling.

    e.g. I was so nervous I got the giggles...
           我紧张得傻笑起来。
    e.g. She had a fit of the giggles.
           她咯咯地笑个不停。

3. 趣事；玩笑
    If you say that something is a giggle, you mean it is fun or is amusing.

    e.g. I might buy one for a friend's birthday as a giggle.
           我可能会买一件送给朋友当生日礼物，逗他开心。