The Collaborative International Dictionary of English v.0.48:

neuter \neu"ter\, v. t.
   To render incapable of sexual reproduction; to remove or
   alter the sexual organs so as to make infertile; to alter; to
   fix; to desex; -- in male animals, to castrate; in female
   animals, to spay.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Spay \Spay\, v. t. [imp. & p. p. Spayed; p. pr. & vb. n.
   Spaying.] [Cf. Armor. spac'hein, spaza to geld, W. dyspaddu
   to geld, L. spado a eunuch, Gr. ?.]
   To remove or extirpate the ovaries of, as a sow or a bitch;
   to castrate (a female animal).
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spay \Spay\, n. [Cf. Spade a spay, Spay, v. t.] (Zool.)
   The male of the red deer in his third year; a spade.
   [1913 Webster] Spayad

WordNet (r) 3.0 (2006):

spay
    v 1: remove the ovaries of; "Is your cat spayed?" [syn: alter,
         neuter, spay, castrate]