A large-scale industrial site where many animals (generally chickens, turkeys,
cattle, or pigs) are confined and treated with hormones and antibiotics to
maximize growth and prevent disease. The animals produce much more waste than the
surrounding land can handle. These operations are associated with various
environmental hazards as well as cruelty to animals.
The government calls these facilities Concentrated (or Confined) Animal Feeding
Operations (CAFOs). The Environmental Protection Agency (EPA) defines a CAFO as
“new and existing operations which stable or confine and feed or maintain
for a total of 45 days or more in any 12-month period more than the number of
animals specified” in categories that they list out. In addition,
“there’s no grass or other vegetation in the confinement area during the normal
growing season.”

Also see: CAFO & AFO

More info:

Legal Issues with Animal Agriculture

Concentrated Animal Feeding Operations Final Ruling — Fact Sheet