To fly, revolve, or move rapidly with a whir. (Merriam – Webster)
(especially of machines) to make a low, soft, continuous sound. (Cambridge Dictionary)
A prolonged soft swish or buzz, as of a motor working or wings flapping. (Collins Dictionary)
(of something rapidly rotating or moving to and fro) make a low, continuous, regular sound. (Oxford Dictionaries)
Whir of grinder.