whirr

Universal Words (especially BrE) (AmE usually whir) verb, noun verb (-rr-) [V] to make a continuous low sound like the parts of a machine moving: The clock began to whirr before striking the hour. noun (also whirring) [usuallysing.] a continuous low sound, for example the sound made by the regular movement of a machine or the wings of a bird: the whirr of a motor * There was a whirring of machinery.