決め込む
1
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)
本人は唯我独尊を決め込んでいるようだけども、周りから見れば単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.
3
to go through with (what one decided to do);to persist in doing;to make up one's mind
私は、議論が終わるのを辛抱強く待つことに決め込んだ。
I decided to bide my time and wait for the argument to finish.
Other forms
決めこむ 【きめこむ】 · 決込む 【きめこむ】 · 極め込む 【きめこむ】