1.
go-home club; students who don't belong to any club
A humorous, self-deprecating term used by Japanese students who are not members of any extracurricular club or team. Structured like a real club name but meaning they simply go straight home after school.
Cultural note
In Japanese schools, extracurricular club activities (部活動) are a major part of student life, and there is social pressure to belong to one. 帰宅部 is a humorous coinage that treats "going home" as if it were an official club, using the standard 部 suffix found in real club names like 野球部 or 美術部.
Usage
Mainly used by and about middle school and high school students. The tone is lighthearted and often self-deprecating.