(1):

(a.) A lever or key acted on by the foot, as in the pianoforte to raise the dampers, or in the organ to open and close certain pipes; a treadle, as in a lathe or a bicycle.

(2):

(a.) A pedal curve or surface.

(3):

(a.) Of or pertaining to a pedal; having pedals.

(4):

(a.) Of or pertaining to the foot, or to feet, literally or figuratively; specifically (Zool.), pertaining to the foot of a mollusk; as, the pedal ganglion.