godan verb (-ru), intransitive verb
shut oneself away; seclude oneself
Describes voluntarily staying inside a room, house, or enclosed space, often for a long time, avoiding social contact. Can imply withdrawal, concentration, or hikikomori-like behavior.
彼は部屋に閉じこもってゲームばかりしている。
He shuts himself in his room and does nothing but play games.
試験前
Before the exam, I holed up in the library and studied.