expression, noun-modifying (irregular)
Fixed prenominal expression meaning 'against the path (of righteousness)'. Used to describe actions, relationships, or desires that are morally wrong or socially unacceptable. Often appears in set phrases like 道ならぬ恋 (forbidden love).
彼は道ならぬ恋に落ちてしまった。
He fell into a forbidden love.
道ならぬ行いをしてはいけない。
You must not do immoral deeds.