但也有多户合住一座四合院的情况，被称为“大杂院”，住户多为普通劳动人民。
I found this in the Standard Course Book of HSK5, section 14.
What is the meaning of 杂院? According to dictionaries (character by character), it means "mixed courtyard", but I don't know, it does not make much sense.
This 知乎 thread sheds some light on the question.
大杂院 is a single word and you don't split it as "a big 杂院". 大 refers to its scale, housing multiple or even tens of families in one courtyard. 杂 (mixed, mingled) refers to its residents who aren't a single, large family and sometimes are even unrelated families, like modern residential areas. This is emphasized in comparison to traditional 四合院 where only one family resides.
