hum
hum \'h*m\ vb or hummed; or hum.ming [ME hummen; akin to MHG hummen to hum, MD hommel bumblebee] 1a: to utter a sound like that of the speech sound /m/ pro longed 1b: to make the natural noise of an insect in motion or a similar sound :: DRONE 1c: to give forth a low continuous blend of sound 2: to be busily active 1: to sing with the lips closed and without articulation 2: to affect or express by humming - hum n