決め込む

きめこむ

to take for granted; to assume; to be convinced (that); to jump to the conclusion (that)

Also written 決めこむ、決込む、極め込む

Meaning

v5mvt
to take for granted; to assume; to be convinced (that); to jump to the conclusion (that)
v5mvt
to pretend (to be); to pose (as); to fancy oneself (to be); to feign (e.g. ignorance)
v5mvt
to go through with (what one decided to do); to persist in doing; to make up one's mind

Example sentences

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.
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.