Tread

n.
  1. A step or stepping; pressure with the foot; a footstep; as, a nimble tread; a cautious tread.
  2. Manner or style of stepping; action; gait; as, the horse has a good tread.
  3. Way; track; path.
  4. The act of copulation in birds.
  5. (Arch.) The upper horizontal part of a step, on which the foot is placed.
  6. (Fort.) The top of the banquette, on which soldiers stand to fire over the parapet.
  7. (Mach.) The chalaza of a bird's egg; the treadle.
  8. (Far.) A bruise or abrasion produced on the foot or ankle of a horse that interferes. See Interfere, 3.
    1. The part of a wheel that bears upon the road or rail.
    2. The part of a rail upon which car wheels bear.