Correct spelling for the English word "eifb" is [ˈa͡ɪfb], [ˈaɪfb], [ˈaɪ_f_b] (IPA phonetic alphabet).
Apologies, but "eifb" does not appear to be an established word or acronym in the English language. It is possible that "eifb" may be a unique acronym, abbreviation, or a term specific to a certain field or context. Without further information or context, it is difficult to provide an accurate definition for this term.
To provide a comprehensive dictionary definition, it is necessary to have at least some basic understanding of the term's meaning, usage, or subject matter. If you can offer additional details or clarify the context in which you encountered "eifb," I would be happy to assist you with a more accurate definition.