(noun) A dog who's primary motivation in life is eating people food from the table. Food dogs are typically fixed and have owners with bad habits of feeding them. Almost 100% of beagles are food dogs.
"Fido is kind of just a food dog now that he's fixed. He doesn't need to impress the ladies so hes always under my feet at the table"
In a nutshell, dogfooding means "using your own product". A product which is being dogfooded tends to be a lot more polished. When a normal user is annoyed by the product, they can't do anything about it. But when a developer is annoyed by the product, they can stop what they are doing and make the product less annoying.
In the past I've always dogfooded new builds for a while before making them
release candidates.