/hʌm ||; hʌm/verb (
humming;hummed)
1 [I] to make a continuous low noise 发出连续低沉的声音；发嗡嗡声: The machine began to hum as I switched it on. 我一开电源，机器就开始发出嗡嗡的声音。
2 [I,T] to sing with your lips closed 哼曲子 ·
You can hum the tune if you don't know the words. 要是不知道歌词，可以哼曲子。
hum noun [sing]
the hum of machinery/distant traffic 机器╱远处往来车辆的嗡嗡声