Webster's Revised Unabridged Dictionary · 1913

Birr

Birr ({not transcribed}) , intransitive verb

[Compare Old English bur, bir, wind, storm wind, from Icelandic byrr wind. Perh. imitative.]

To make, or move with, a whirring noise, as of wheels in motion.

Birr , noun

1.
A whirring sound, as of a spinning wheel.
2.
A rush or impetus; force.