Source : Webster's Revised Unabridged Dictionary (1913)

Treadle \Trea"dle\, n. [OE. tredyl a step, AS. tredel. See
   {Tread}.]
   1. The part of a foot lathe, or other machine, which is
      pressed or moved by the foot.

   2. (Biol.) The chalaza of a bird's egg; the tread.

Source : WordNet®

treadle
     n : a lever that is operated with the foot [syn: {pedal}, {foot
         pedal}, {foot lever}]
     v 1: tread over; "the brickmaker treadles over clay to pick out
          the stones"
     2: operate (machinery) by a treadle