Webster's Revised Unabridged Dictionary · 1913

Euthanasia

Euthanasia , noun

[New Latin, from Greek {not transcribed}; e'y^ well + {not transcribed} death, {not transcribed}, {not transcribed}, to die: compare French euthanasie.]

1.
An easy death; a mode of dying to be desired.
An euthanasia of all thought. — Hazlitt
The kindest wish of my friends is euthanasia. — Arbuthnot
2.
the act or process of putting to death for humane purposes; -- used to refer to the killing of animals in order to relieve or avoid pain.