Main entry: whir, whirr, whirring, birr
Definition: sound of something in rapid motion
Usage: whir of a bird's wings; the whir of the propellers
Definition: make a vibrant sound, as of some birds
Main entry: purr, birr, whir, whirr, whiz, whizz
Definition: make a soft swishing sound
Usage: the motor whirred; the car engine purred