hum

(noun) the state of being or appearing to be actively engaged in an activity. Synonyms: busyness. Examples: "They manifested all the busyness of a pack of beavers." "There is a constant hum of military preparation."

(noun) 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. Synonyms: Harkat-ul-Mujahidin, HUM, Harkat ul-Ansar, HUA, Harkat ul-Mujahedeen, Al Faran, Movement of Holy Warriors.

(noun) a humming noise. Synonyms: humming. Example: "The hum of distant traffic."

(verb) sing with closed lips. Example: "She hummed a melody."

(verb) be noisy with activity. Synonyms: buzz, seethe. Example: "This office is buzzing with activity."

(verb) sound with a monotonous hum. Synonyms: thrum.

(verb) make a low continuous sound. Example: "The refrigerator is humming."