To become deeply absorbed or engrossed in something, forgetting other matters; to devote oneself completely to an activity.
彼は研究に没頭して夜遅くまで実験を続けた。
He was absorbed in his research and continued experiments until late at night.
休日は読書に没頭して過ごした。
I spent the day off engrossed in reading.
ゲームに没頭しすぎて宿題を忘れた。
I got so absorbed in the game that I forgot my homework.