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The standard of identity is from the Code of Federal Regulations, title 9, section 319.29.
Etymology from Wiktionary, CC BY-SA 4.0.
partially defatted pork fatty tissue
Today it means: Fresh pork fatty tissue, excluding skin, that has been rendered at a temperature not more than 120 degrees Fahrenheit and is pinkish, fresh-looking, and fresh-smelling. Full definition →