.... (Arch.) One in a flight of steps which are parallel to each other(as in ordinary stairs), as distinguished from a winder. 5. The pair of arms attached to the spindle of a spinning frame, over which the thread passes to the bobbin; -- so called from their swift revolution. See Fly, n., 11. 6. The fan wheel that rotates the cap of a windmill as the wind veers. Internat. Cy...