英汉词典

1. 发出连续而低沉的声音;发嗡嗡声
    If something hums, it makes a low continuous noise.

    e.g. The birds sang, the bees hummed...
           鸟儿叫，蜂儿鸣。
    e.g. Within five hours, the equipment will be humming away again...
           用不了5小时，设备就又能嗡嗡地运转了。

2. 哼（曲子）
    When you hum a tune, you sing it with your lips closed.

    e.g. She was humming a merry little tune...
           她哼着一支欢快的小曲儿。
    e.g. He hummed to himself as he opened the trunk.
           他独自哼着曲子打开了车子的后备箱。