* A pig kept in a bar: This is a playful or humorous way to describe a pig that might be a pet or mascot in a bar or pub. It's unlikely to be a real thing, but it could be a fun story or a joke.
* A pig that's "barred" from something: This could be a playful way to describe a pig that's not allowed somewhere, perhaps a farm animal that's not allowed in a house.
* A pig with specific markings: It's possible someone might use "bar pig" to describe a pig with distinct markings, like stripes or patches, similar to how a "piebald" horse has patches of color. This wouldn't be a standard term, though.
If you heard the term "bar pig" in a specific context, please provide more information so I can give a more accurate answer.