A kitchen door or back/service entrance of a house, used for deliveries, taking out trash, or everyday entry and exit.
配達の人は勝手口から荷物を入れてくれた。
The delivery person brought the package in through the back kitchen door.
ゴミは朝、勝手口のところに出しておいてください。
Please put the trash out by the back door in the morning.
子どもが勝手口から遊びに出て行った。
The child went out to play through the service door.
The entrance used by the host or attendants in a tea-ceremony room (tea-ceremony entrance), separate from the guest entrance.
茶会では亭主が勝手口から道具を運び入れた。
At the tea gathering, the host carried in the utensils through the tea-ceremony entrance.
茶道の作法では勝手口の使い方にも決まりがある。
In the manners of the tea ceremony, there are rules about how to use the tea-ceremony entrance.