A part of a molecule, especially a toxin or drug molecule, which enables it to bind to a cell or to another substance; a binding site; a receptor. Now frequently historical with reference to the theories of Paul Ehrlich.
Of the nature of a haptophore; haptophoric. Now chiefly historical with reference to the theories of Paul Ehrlich.
Late 19th century. From German haptophor, adjective from ancient Greek ἅπτειν to fasten + German -o- + -phor.