-raf, -rȧf noun
Etymology: International Scientific Vocabulary plethysmo- (from Greek plēthysmos multiplication, increase, from plēthynein to increase, from plēthys, plēthos mass, magnitude) + -graph; originally formed as Italian pletismografo
: an instrument for determining and registering variations in the size of an organ or limb and in the amount of blood present or passing through it