決め込む

Meanings

1. Godan verb (-mu), Transitive

   to take for granted; to assume; to be convinced (that); to jump to the conclusion (that)
2. to pretend (to be); to pose (as); to fancy oneself (to be); to feign (e.g. ignorance)
3. to go through with (what one decided to do); to persist in doing; to make up one's mind

Forms

• 私わたしは、議論ぎろんが終おわるのを辛抱強しんぼうづよく待まつことに決きめ込こんだ。

  I decided to bide my time and wait for the argument to finish.

• 本人ほんにんは唯我独尊ゆいがどくそんを決きめ込こんでいるようだけども、周まわりから見みれば単たんなるわがままだよね。

  He's completely convinced of his own greatness but to the people around him he's just a selfish jerk.