noun
wealthy person or family
Refers to a person or family of substantial wealth, often with connotations of established, land-based or inherited fortune rather than newly acquired riches. Somewhat formal or literary.
彼は地元の素封家の出身だ。
He comes from a local wealthy family.
その美術館は素封家の寄付で建てられた。
The museum was built with donations from a wealthy patron.
金持ち is a casual, everyday word for a rich person, whereas 素封家 is formal and often implies inherited wealth.
The term 素封家 is composed of 素 (plain, unadorned) and 封 (fief, enfeoffment) and 家 (house, family). It originally referred to a family that, despite lacking official rank or title, possessed wealth comparable to that of a feudal lord. The exact historical derivation is uncertain, but the word is conventionally associated with established, land-based wealth.