Source : Webster's Revised Unabridged Dictionary (1913)

Cardiograph \Car"di*o*graph\, n. [Gr. kardi`a heart + -graph.]
   (Med.)
   An instrument which, when placed in contact with the chest,
   will register graphically the comparative duration and
   intensity of the heart's movements.

Source : WordNet®

cardiograph
     n 1: medical instrument that records electric currents associated
          with contractions of the heart [syn: {electrocardiograph}]
     2: a medical instrument that measures the mechanical force of
        cardiac contractions and the amount of blood passing
        through the heart during a specified period by measuring
        the recoil of the body as blood is pumped from the
        ventricles [syn: {ballistocardiograph}]