(ˌ)dərˈmad.əˌgraf, ˈdərməd.ə- noun
Etymology: dermat- + -graph
: an instrument for producing markings on the skin: as
a. : a crayon used by surgeons to outline internal organs on the body surface
sketch the outline of the liver with a dermatograph on the abdominal skin
b. : a crayon used to test for allergies