1. 无意中说;随口说
    If you throw in a remark when having a conversation, you add it in a casual or unexpected way.

    e.g. Occasionally Farling threw in a question.
           法林有时会突然冒出个问题。

2. 免费赠送;额外奉送
    If a person who is selling something throws in something extra, they give you the extra thing and only ask you to pay for the first thing.

    e.g. Pay ￡
4. 80 for larger prints and they throw in a free photo album...
           付
4. 8 英镑冲印更大尺寸的照片就会获赠一本相册。
    e.g. They were offering me a weekend break in Paris — with free beer thrown in.
           他们让我去巴黎休息一个周末——外加免费啤酒。

verb

1. to insert between other elements

    e.g. She interjected clever remarks

    Synonym: interjectcome ininterposeput ininject

2. give up in the face of defeat of lacking hope
    admit defeat

    e.g. In the second round, the challenger gave up

    Synonym: drop outgive upfall by the waysidedrop by the waysidethrow in the towelquitchuck up the sponge

3. add as an extra or as a gratuity