1. 
[syn: whir, whirr, whirring, birr]
ADJECTIVE (1)
1.  like the sound of rapidly vibrating wings; 
The Collaborative International Dictionary of English v.0.48:
Whir \Whir\, v. i. [imp. & p. p. Whirred; p. pr. & vb. n.
   Whirring.] [Perhaps of imitative origin; cf. D. hvirre to
   whirl, and E. hurr, hurry, whirl. ???.]
   To whirl round, or revolve, with a whizzing noise; to fly or
   more quickly with a buzzing or whizzing sound; to whiz.
   [1913 Webster]
         The partridge bursts away on whirring wings. --Beattie.
   [1913 Webster]
WordNet (r) 3.0 (2006):
whirring
    adj 1: like the sound of rapidly vibrating wings
    n 1: sound of something in rapid motion; "whir of a bird's
         wings"; "the whir of the propellers" [syn: whir, whirr,
         whirring, birr]