Euthanasia is the act of bringing about the death of a hopelessly ill and suffering person in a relatively quick and painless way for reasons of mercy.
Definition Two:
Euthanasia is the act of killing a person who is terminally ill (active euthanasia) or allowing such a person to die by withholding treatment (passive euthanasia). Usually the act is claimed to be an act of mercy.
Euthanasia is the practice of 'mercy killing', terminating a painfilled life with a painless death.