Definition & Meaning of "jailhouse lawyer"in English

What does "jailhouse lawyer" mean in prison slang?

The structure combines "jailhouse" with "lawyer" (a legal professional), forming a compound noun that ironically elevates an amateur to a professional title. It is used to describe an inmate who provides legal advice, often unqualified, or represents themselves and others in legal matters using research from law books, prior experience, or sheer confidence. People typically refer to someone as a "jailhouse lawyer" when they file motions, write appeals, or argue cases without formal training, sometimes successfully but often not.