The Collaborative International Dictionary of English v.0.48:

Eunuch \Eu"nuch\, n. [L. eunuchus, Gr. ?, prop., keeping or
   guarding the couch; ? couch, bed, + ? to have, hold, keep.]
   A male of the human species castrated; commonly, one of a
   class of such persons, in Oriental countries, having charge
   of the women's apartments. Some of them, in former times,
   gained high official rank. Eunuch

The Collaborative International Dictionary of English v.0.48:

Eunuch \Eu"nuch\, Eunuchate \Eu"nuch*ate\, v. t. [L. eunuchare.]
   To make a eunuch of; to castrate. as a man. --Creech. Sir. T.
   Browne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

eunuch
    n 1: a man who has been castrated and is incapable of
         reproduction; "eunuchs guarded the harem" [syn: eunuch,
         castrate]

Easton's 1897 Bible Dictionary:

Eunuch
   literally bed-keeper or chamberlain, and not necessarily in all
   cases one who was mutilated, although the practice of employing
   such mutilated persons in Oriental courts was common (2 Kings
   9:32; Esther 2:3). The law of Moses excluded them from the
   congregation (Deut. 23:1). They were common also among the
   Greeks and Romans. It is said that even to-day there are some in
   Rome who are employed in singing soprano in the Sistine Chapel.
   Three classes of eunuchs are mentioned in Matt. 19:12.