Definition of "eunuch"

Semiramis was the first woman to invent eunuchs and women have had sympathy for them ever since; […] and women can tell them what they can't tell other men.

1922, Michael Arlen, “2/1/2”, in “Piracy”: A Romantic Chronicle of These Days‎

He ſhall be made a chaſte and luſtleſſe Eunuch,And in my Sarell tend my Concubines

c. 1587–1588, [Christopher Marlowe], Tamburlaine the Great. […] The First Part […], 2nd edition, part 1, London: […] [R. Robinson for] Richard Iones, […], published 1592; reprinted as Tamburlaine the Great (A Scolar Press Facsimile), Menston, Yorkshire, London: Scolar Press, 1973, Act III, scene iii