also: やまいこうもうにいる
expression, godan verb (-ru)
become seriously ill; catch an incurable illness
Classical expression meaning the illness has reached a critical, often incurable stage. Used in formal or literary contexts.
彼は病膏肓に入り、医者も手の施しようがなかった。
He became seriously ill, and even the doctors could do nothing for him.
expression, godan verb (-ru)
become a slave of a habit
Figurative extension: a bad habit or obsession has taken such deep root that it is like an incurable disease. Rare, literary usage.
彼はギャンブルが病膏肓に入ってしまい、借金が膨らむばかりだ。
He has become a slave to gambling, and his debts just keep growing.