noun
bad fortune; misfortune
Refers to an unlucky fate or unfortunate circumstances, often with a slightly literary or formal tone.
彼は非運にも若くして亡くなった。
He unfortunately passed away at a young age.
非運を嘆いても仕方がない。
There's no use lamenting your misfortune.
不運 is the more common word for 'bad luck' or 'misfortune'; 非運 is less frequent and carries a slightly more literary or fate-oriented nuance.
Compound of 非 (hi, 'not') and 運 (un, 'fortune'). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning of 'bad fortune'.