noun
public toilet; shared lavatory
Refers to a toilet facility shared by multiple people, such as in a dormitory, apartment building, or public space. Often used interchangeably with 公衆便所.
See also: 公衆便所 (こうしゅうべんじょ)
このアパートは共同便所なので、掃除当番がある。
This apartment has a shared toilet, so there is a cleaning duty roster.
noun
slut; promiscuous woman
Vulgar slang likening a woman to a public toilet. Strongly derogatory; avoid in polite conversation.
See also: 公衆便所
あいつは共同便所だって、陰で言われてるらしい。
I hear she's being called a slut behind her back.