Swill is food for animals in liquid or partly liquid form.
The term can also be used as an extremely derogatory label for any drink meant for human consumption perceived as unpalatable or nearly so.
Historically pig farmers arranged collection of swill, e.g. by means of swill bins. The grease was skimmed off the swill tanks and sold for further processing, while the remaining swill was processed into pig food.
During the 2001 United Kingdom foot-and-mouth outbreak it was thought that unprocessed pig swill was a key link in the chain of the infection, and it was banned in Great Britain. In 2003 the ban was expanded to the whole European Union.