1. 打哈欠
    If you yawn, you open your mouth very wide and breathe in more air than usual, often when you are tired or when you are not interested in something.

    e.g. She yawned, and stretched lazily...
           她打了个哈欠，伸了个懒腰。
    e.g. They looked bored and yawned at the speeches.
           他们看起来已经厌倦了这些演讲，直打哈欠。

2. 乏味的事物;枯燥的事物
    If you describe something such as a book or a film as a yawn, you think it is very boring

yawn的翻译

    e.g. The debate was a mockery. A big yawn...
           这场辩论实在可笑。简直是无聊透顶。
    e.g. The concert was a predictable yawn.
           果不其然，那场音乐会很乏味。

3. （裂隙或缺口）裂开，豁开
    A gap or an opening that yawns is large and wide, and often frightening.

    e.g. The gulf between them yawned wider than ever...
           他们之间的隔阂比以往任何时候都要深。
    e.g. Liddie's doorway yawned blackly open at the end of the hall.
           走廊尽头利迪的门黑洞洞地敞开着。