n.1 a person who gives or donates something (e.g. to a charity).
2 one who provides blood for a transfusion, semen for insemination, or an organ or tissue for transplantation.
3 Chem. an atom or molecule that provides a pair of electrons in forming a coordinate bond.
4 Physics an impurity atom in a semiconductor which contributes a conducting electron to the material.
Phrases and idioms:
donor card an official card authorizing use of organs for transplant, carried by the donor.
Etymology: ME f. AF donour, OF doneur f. L donator -oris f. donare give