noun, noun which may take the genitive case particle 'no'
everlasting; eternal; imperishable
A yojijukugo emphasizing that something will never decay or perish; often used for abstract concepts like fame, truth, or spirit.
彼の功績は不朽不滅のものとして語り継がれるだろう。
His achievements will be passed down as something eternal.
この作品は不朽不滅の名作だ。
This work is an immortal masterpiece.
不滅 alone means 'indestructible' or 'immortal'; 不朽不滅 combines both nuances for stronger effect.
A yojijukugo composed of 不朽 (immortal, undying) and 不滅 (indestructible, imperishable), reinforcing the idea of eternal endurance.