intransitive verb hummed, humming hum′·ming

1. to make a low, continuous, murmuring sound like that of a bee or a motor
2. to sing with the lips closed, not producing words
3. to give forth a confused, droning sound a room humming with voices
4. Informal to be busy or full of activity

Etymology: ME hummen, of echoic orig., as in Ger hummel, bumblebee, MDu hommeln, hum

transitive verb

1. to sing (a tune, etc.) with the lips closed
2. to produce an effect on by humming to hum a child to sleep

noun

1. the act of humming
2. a continuous, murmuring sound