One who makes a donation. / (chemistry) A group or molecule that donates either a radical, electrons or a moiety in a chemical reaction. Compare acceptor.

plural of donor

(medicine) A person with blood type O, which lacks antigens and is therefore compatible with all other blood types, allowing them to donate blood to any other person.

plural of universal donor

A person (living or dead) from whom an organ is removed in order to be transplanted into another person. / (chiefly US, slang) A motorcyclist, especially one who does not wear a protective helmet.

(US) A person who makes political contributions provided by an anonymous third party

A man who donates sperm, usually anonymously, to a sperm bank or fertility clinic.

plural of blood donor

A person who donates blood for use in transfusion.

plural of organ donor