noun, noun or participle which takes 'suru'
diligent effort; hard work; strenuous endeavor
A yojijukugo describing the act of working hard and persevering through difficulties. Often used in formal or written contexts to praise dedication.
彼の刻苦精励の末の成功は、多くの人に感動を与えた。
His success after years of diligent effort moved many people.
学生時代は刻苦精励して研究に打ち込んだ。
During my student days, I devoted myself to research with strenuous effort.