Any inarticulate and buzzing sound

The confused noise of a crowd or of machinery, etc., heard at
a distance; as, the hum of industry.

To sing with shut mouth; to murmur without articulation; to
mumble; as, to hum a tune.

A low monotonous noise, as of bees in flight, of a swiftly
revolving top, of a wheel, or the like; a drone; a buzz.

To express satisfaction with by humming.

To have the sensation of a humming noise; as, my head hums,
– a pathological condition.

To make an inarticulate sound, like h’m, through the nose
in the process of speaking, from embarrassment or a affectation; to
hem.

To make a nasal sound, like that of the letter m prolonged,
without opening the mouth, or articulating; to mumble in monotonous
undertone; to drone.

To express satisfaction by a humming noise.

To flatter by approving; to cajole; to impose on; to
humbug.