Hum (verb)

1. To make a low continuous sound, often by vibrating the lips or the vocal cords.
2. To make a low sound or buzz, often caused by mechanical vibration or electrical current.

Origin:

Derived from the middle english word hummen, meaning 'to make a low droning sound'.

Examples:

1. The children hummed a lullaby as they went to sleep.
2. The machine was humming softly in the background.
3. She hummed a tune as she worked in the garden.
4. The room was filled with the hum of voices.
5. The humming of the electric fan filled the room with white noise.