humming

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

(noun) the act of singing with closed lips.

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

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

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

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