Толковый словарь английского языка - hum

I. verb (~med; ~ming) Etymology: Middle English ~men; akin to Middle High German ~men to ~, Middle Dutch hommel bumblebee Date: 14th century intransitive verb 1. to utter a sound like that of the speech sound m prolonged, to make the natural noise of an insect in motion or a similar sound ; drone, to give forth a low continuous blend of sound, 2. to be busily active , to run smoothly , transitive verb to sing with the lips closed and without articulation, to affect or express by ~ming , ~ noun ~mable adjective see: hem