granny flat
noun🔊/ˈɡræni flæt/
🔊/ˈɡræni flæt/
(British English) (also in-law apartment, mother-in-law apartment, in-law suite all North American English)
(informal)a set of rooms for an old person, especially in a relative’s house （尤指亲戚家中的）老人套间