A man who has been castrated and is incapable of reproduction:
— Eunuchs guarded the harem.

synonym: castrate.

Roget 158: impotence; inability, disability; disablement, impuissance, imbecility; incapacity, incapability; inaptitude, ineptitude, incompetence, unproductivity^†; indocility^†; invalidity, disqualification; inefficiency, wastefulness.    telum imbelle [Lat.], brutum fulmen [Lat.], blank, blank cartridge, flash in the pan, vox et proeterea nihil [Lat.], dead letter, bit of waste paper, dummy; paper tiger; Quaker gun.    inefficacy etc. (inutility) 645^†; failure etc. 732.    helplessness etc. adj.; prostration, paralysis, palsy, apoplexy, syncope, sideration^†, deliquium [Lat.], collapse, exhaustion, softening of the brain, inanition; emasculation, orchiotomy [Med.], orchotomy [Med.].    cripple, old woman, muff, powder puff, creampuff, pussycat, wimp, mollycoddle; eunuch.    ... show more

Dutch: castraat, eunuch, haremwachter, kamerling
Polish: kastrat