“Breeder” is a slang term that gay people use when describing straight people in either a derogatory or humorous manner. It is drawn from animal husbandry; implying that heterosexual sexual contact has more to do with reproduction than anything else.
1. a derogatory term used to describe straight people in light of their ability to reproduce
: “Look at this place. It used to be so cool, and now it’s filled with a bunch of breeders.”