humming (Noun) — A humming noise. ex. "the humming of distant traffic"
humming (Noun) — The act of singing with closed lips.
humming (Verb) — Sing with closed lips. ex. "She hummed a melody"
humming (Verb) — Be noisy with activity. ex. "This office is humming with activity"
humming (Verb) — Sound with a monotonous hum.
humming (Verb) — Make a low continuous sound. ex. "The refrigerator is humming"
humming (Verb) — Smell badly and offensively.