hum hum /ˈhʌm/

interjection

1. () Vocalizations indicating uncertainty or reservation.  ( ahem , hum , h'm , hmm )
   Vocalizations indicating uncertainty or reservation.
   

noun

1. A humming noise  ( hum , humming )
   a humming noise
    The hum of distant traffic
   the hum of distant traffic
   
2. The state of being or appearing to be actively engaged in an activity  ( 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
   they manifested all the busyness of a pack of beavers
    There is a constant hum of military preparation
   there is a constant hum of military preparation
   

verb

1. () Sing with closed lips  ( hum )
   sing with closed lips
    She hummed a melody
   She hummed a melody
   
2. Make a low continuous sound  ( hum )
   make a low continuous sound
    The refrigerator is humming
   The refrigerator is humming
   
3. Sound with a monotonous hum  ( hum , thrum )
   sound with a monotonous hum
   
4. Be noisy with activity  ( hum , seethe , buzz )
   be noisy with activity
    This office is buzzing with activity
   This office is buzzing with activity
   

 HUM

noun

1. 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  ( Al Faran , Harkat ul-Ansar , Harkat ul-Mujahedeen , Harkat-ul-Mujahidin , HUA , HUM , Movement of Holy Warriors , Harkat-ul-Mujahideen )
   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