noun
lingering illness; chronic ill health; long-term malaise of uncertain origin
Medical term for a persistent, vague illness without a clear diagnosis; often implies a state of being unwell over a long period.
彼はぶらぶら病で、もう半年も仕事を休んでいる。
He has been off work for half a year with a lingering illness.
慢性病 is a general term for chronic disease, while ぶらぶら病 specifically refers to a lingering illness of uncertain origin.
The term ぶらぶら病 is composed of the mimetic word ぶらぶら (onomatopoeia for hanging loosely or idling) and 病 (illness), suggesting an illness that lingers without clear cause or resolution. The exact origin is uncertain.