This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. Having been subjected to a superfatting treatment.

Containing more fat than can combine with the amount of alkali present: noting certain soaps used for medicinal purposes.

adj. (of soap) containing extra unsaponified fat

"Stick to unscented, superfatted soaps made from natural ingredients including cocoa butter, aloe, jojoba oil, and wheat-germ oil."

fat    fatty