birr (
http://definr.com/birr)
n 1: the basic unit of money in Ethiopia; equal to 100 cents
2: sound of something in rapid motion: "whir of a bird's
wings"; "the whir of the propellers" [syn:
whir,
whirr,
whirring]
v : make a soft swishing sound, as of a motor working or wings
flapping [syn:
whizz,
whiz,
whirr,
whir,
purr]