noun
backbone; spirit of defiance; unyielding spirit
Refers to a strong, independent mindset that refuses to submit to authority or conform. Often used in positive contexts to describe someone with moral courage and a rebellious, principled character.
彼は反骨の精神を持って、上司の不正に立ち向かった。
With a spirit of defiance, he stood up to his boss's wrongdoing.
反骨の精神を忘れずに、自分の信念を貫きたい。
I want to stick to my beliefs without losing my rebellious spirit.
Compound of 反骨 (rebellious spirit, from 反 'anti-' + 骨 'bone') and 精神 (spirit, mind). The phrase literally means 'the spirit of a rebellious bone', metaphorically describing an unyielding character.