bleeder

(blēˈdər)

1. A person, such as a hemophiliac, who bleeds freely or is subject to frequent hemorrhages.
2. a. Slang A blood vessel from which there is uncontrolled bleeding.
   b. A blood vessel severed by trauma or surgery that requires cautery or ligature to arrest the flow of blood.
3. A person who draws blood from another; a phlebotomist.