Source : WordNet®

whirr
     n : sound of something in rapid motion; "whir of a bird's
         wings"; "the whir of the propellers" [syn: {whir}, {whirring},
          {birr}]
     v 1: make a soft swishing sound; "the motor whirred"; "the car
          engine purred" [syn: {whizz}, {whiz}, {whir}, {birr}, {purr}]
     2: make a vibrant sound, as of some birds [syn: {churr}]