shut somebody in (something) phrasal verb ( see also ↑ shut )
a) if you shut someone in a room, you close the door and stop them from getting out:
Her parents shut her in an upstairs room.
He pushed the dogs into the breakfast room and shut them in.
b) shut yourself in (something) if you shut yourself in a room, you close the door and stay in there, and often stop other people from coming in:
Ellie darted back to her room and shut herself in.
He shut himself in his room and wrote letters.