Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
spay (v.)
To spay a female animal is to remove its ovaries; the principal parts of this transitive and intransitive verb are spay, spayed, spayed. The variously spelled spade and spayd (for the infinitive and present tense) and spayded (for the past tense and past participle) are Substandard; spayded represents a Substandard pronunciation as well.
