Noun

1. A person who breeds plants or animals professionally.
2. (gay slang; derogatory) A heterosexual; i.e. one whose sexual intercourse can lead to breeding.
3. A type of nuclear reactor that creates material suitable for the production of atomic weapons. (See Wikipedia's article on fast breeder reactors.)
4. a person who has had or who is capable of having children; a person who is focussed on the rearing of their own children.

   Quotations:

   • 1729:"The number of souls in this kingdom being usually reckoned one million and a half, of these I calculate there may be about two hundred thousand couple whose wives are breeders; from which number I subtract thirty thousand couples who are able to maintain their own children, although I apprehend there cannot be so many, under the present distresses of the kingdom; but this being granted, there will remain an hundred and seventy thousand breeders." — Jonathan Swift A Modest Proposal

   Usage note: This meaning is generally either an ironic usage (as in the Swift quotation) or an intentionally offensive usage (by implying that parenthood is the same as animal husbandry).