hum

n : 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"