절치부심이 · 절치부심을
gnashing one's teeth with resolve, burning determination after a defeat
Example
지난 대회에서 진 뒤 그는 절치부심하며 연습했어요.
After losing the last tournament, he practiced with fierce determination.
Word parts
절 grind+치 teeth+부 rot+심 heart
Literally 'grinding teeth and rotting the heart' — seething anger turned into resolve.