Etymology: (1300–50; ME; ult. imit.; cf. MHG hummen to hum)
Definition of 'HUM'
Princeton's WordNet
1. (noun)busyness, hum the state of being or appearing to be actively engaged in an activity "they manifested all the busyness of a pack of beavers"; "there is a constant hum of military preparation"
2. (noun)Harkat-ul-Mujahidin, HUM, Harkat ul-Ansar, HUA, Harkat ul-Mujahedeen, Al Faran, Movement of Holy Warriors an Islamic fundamentalist group in Pakistan that fought the Soviet Union in Afghanistan in the 1980s; now operates as a terrorist organization primarily in Kashmir and seeks Kashmir's accession by Pakistan
3. (verb)hum, humming a humming noise "the hum of distant traffic"
4. (verb)hum sing with closed lips "She hummed a melody"
5. (verb)hum, buzz, seethe be noisy with activity "This office is buzzing with activity"
6. (verb)hum, thrum sound with a monotonous hum
7. (verb)hum make a low continuous sound "The refrigerator is humming"
1. (verb)hum to sing without words and with your mouth closed to hum a tune; She hummed as she worked.
2. hum to make a continuous low sound The computer hummed in the corner.
3. hum (of a place) to be full of activity or emotion Downtown was humming with Christmas shoppers.
Definition of 'HUM'
Webster Dictionary
1. (noun)HUM a low monotonous noise, as of bees in flight, of a swiftly revolving top, of a wheel, or the like; a drone; a buzz
2. (noun)HUM any inarticulate and buzzing sound
3. (noun)HUM the confused noise of a crowd or of machinery, etc., heard at a distance; as, the hum of industry
4. (noun)HUM a buzz or murmur, as of approbation
5. (noun)HUM an imposition or hoax
6. HUM an inarticulate nasal sound or murmur, like h'm, uttered by a speaker in pause from embarrassment, affectation, etc
7. HUM a kind of strong drink formerly used
8. HUM ahem; hem; an inarticulate sound uttered in a pause of speech implying doubt and deliberation
9. (verb)HUM to make a low, prolonged sound, like that of a bee in flight; to drone; to murmur; to buzz; as, a top hums
10. (verb)HUM 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
11. (verb)HUM to make an inarticulate sound, like h'm, through the nose in the process of speaking, from embarrassment or a affectation; to hem
12. (verb)HUM to express satisfaction by a humming noise
13. (verb)HUM to have the sensation of a humming noise; as, my head hums, -- a pathological condition
14. (verb)HUM to sing with shut mouth; to murmur without articulation; to mumble; as, to hum a tune
15. (verb)HUM to express satisfaction with by humming
16. (verb)HUM to flatter by approving; to cajole; to impose on; to humbug
Definitions of HUM 
Afrikaans: neurie
Arabic: يُرَنِّمُ ، يُدَنْدِنُ
Bulgarian: тананикам
Brazilian: cantarolar
Czech: broukat
German: summen
Danish: nynne
Greek: σιγομουρμουρίζω
Spanish: tararear, canturrear
Estonian: ümisema
Farsi: وزوزكردن
Finnish: hyräillä
French: fredonner
Hebrew: לְזַמזֵם
Hindi: गुनगुनाना
Croatian: pjevušiti(zatvorenih usta
Hungarian: zümmög
Indonesian: menggumam
Icelandic: humma; raula með lokaðan 
Italian: canticchiare
Japanese: ハミングする
Korean: 콧노래르 부르다
Lithuanian: niūniuoti
Latvian: dungot
Malay: bersenandung
Dutch: neurien
Norwegian: nynne, småsynge
Polish: nucić, śpiewać mormorando
Persian: وزوزكردن
Pashto: بز بز کول
Portuguese: cantarolar
Romanian: a fredona
Russian: мурлыкать
Slovak: nôtiť si, pohmkávať
Slovenian: brundati
Serbian: pevušiti
Swedish: nynna
Thai: ฮัมเพลงโดยไม่เปิดปาก
Turkish: mırıldanmak
Taiwanese: 哼唱
Ukrainian: мугикати
Urdu: گنگنانا
Vietnamese: ngậm miệng ngân nga
Chinese: 哼曲子
