Synonyms for Hum (same or very similar meaning)
WordNet sense 1 (the state of being or appearing to be actively engaged in an activity):
busyness
WordNet sense 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):
Harkat-ul-Mujahidin, HUA, Al Faran, Harkat ul-Ansar, Harkat ul-Mujahedeen, Movement of Holy Warriors
WordNet sense 3 (a humming noise):
humming
WordNet sense 4 (be noisy with activity):
buzz, seethe
WordNet sense 5 (sound with a monotonous hum):
thrum
From the ODE community, based on WordNet
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