The word "BMNJ" does not have a standard meaning in the English language, and it is not possible to provide an IPA phonetic transcription to explain its spelling. "BMNJ" is likely a non-standard combination of letters used as an acronym or abbreviation in a specific context or subject matter. It is important to use context and clarification to ensure clear communication when using unfamiliar or unconventional words, such as "BMNJ."