A person who breeds plants or animals (professionally).
Ellipsis of breeder reactor, a type of nuclear reactor that creates more fissile material than it consumes, often used for the production of atomic weapons.
A 40-gallon fish tank, sometimes used to breed fish that is low in height and wide in length, typically measuring 36 inches long, 18 inches wide, and 16 inches high, making it and shallower than a typical 40-gallon aquarium.
Esimerkit
Since the breeders started coming here, you can never tell who likes cock.
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.