noun
rare; extraordinary; unparalleled
Describes a person of exceptional talent or achievement that appears only once in a generation. Often used in formal or literary contexts, especially in phrases like 不世出の英雄 (a rare, unparalleled hero).
彼は不世出の天才と呼ばれている。
He is called a once-in-a-generation genius.
不世出の名選手が引退した。
The unparalleled great player has retired.
空前絶後 means 'unprecedented and never to be repeated', often used for events or achievements, whereas 不世出 is typically used for exceptional individuals.
Compound of 不 (not), 世 (generation, world), and 出 (appear). Literally 'not appearing in a generation', meaning so rare that one does not appear in an ordinary era.