没頭 ぼっとう
bottō

Noun
Suru Verb

1. immersing oneself in; being absorbed in; devoting oneself to; giving oneself up entirely to

Intransitive
かれはわれを わすれて研究 けんきゅう没頭 ぼっとうした。
karewa wareo wasurete kenkyūni bottō shita.
He lost himself in his studies.