Webster's Revised Unabridged Dictionary · 1913

Hum

Hum (hum) , intransitive verb

[Of imitative origin; compare German hummen, Dutch hommelen. r15.]

1.
To make a low, prolonged sound, like that of a bee in flight; to drone; to murmur; to buzz; as, a top hums. — P. Fletcher
Still humming on, their drowsy course they keep. — Pope
2.
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.
The cloudy messenger turns me his back, And hums. — Shakespeare
3.
To make an inarticulate sound, like h'm, through the nose in the process of speaking, from embarrassment or a affectation; to hem.
4.
To express satisfaction by a humming noise.
Here the spectators hummed. — Trial of the Regicides

Formerly the habit of audiences was to express gratification by humming and displeasure by hissing.

5.
To have the sensation of a humming noise; as, my head hums, -- a pathological condition.

Hum , transitive verb

1.
To sing with shut mouth; to murmur without articulation; to mumble; as, to hum a tune.
2.
To express satisfaction with by humming.
3.
To flatter by approving; to cajole; to impose on; to humbug. [Colloquial & Low]

Hum , noun

1.
A low monotonous noise, as of bees in flight, of a swiftly revolving top, of a wheel, or the like; a drone; a buzz.
The shard-borne beetle with his drowsy hums. — Shakespeare
2.
Any inarticulate and buzzing sound
(a)
The confused noise of a crowd or of machinery, etc., heard at a distance; as, the hum of industry.
But 'midst the crowd, the hum, the shock of men. — Byron
(b)
A buzz or murmur, as of approbation. — Macaulay
3.
An imposition or hoax.
4.
An inarticulate nasal sound or murmur, like h'm, uttered by a speaker in pause from embarrassment, affectation, etc.
These shrugs, these hums and ha's. — Shakespeare
5.
A kind of strong drink formerly used. [Obsolete] — Beau. & Fl
Collocations (1)
Venous hum , See under Venous.

Hum , interjection

[Compare Hem, interj.]

Ahem; hem; an inarticulate sound uttered in a pause of speech implying doubt and deliberation. — Pope