hum
     n 1: 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" [syn: {busyness}]
     2: 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 [syn: {Harkat-ul-Mujahidin},
         {Harkat ul-Ansar}, {HUA}, {Harkat ul-Mujahedeen}, {Al
        Faran}, {Movement of Holy Warriors}]
     3: a humming noise; "the hum of distant traffic" [syn: {humming}]
     v 1: sing with closed lips; "She hummed a melody"
     2: be noisy with activity; "This office is buzzing with
        activity" [syn: {buzz}, {seethe}]
     3: sound with a monotonous hum [syn: {thrum}]
     4: make a low continuous sound; "The refrigerator is humming"
     [also: {humming}, {hummed}]
Source: WordNet® 2.0