What is the meaning of h-index for a journal? What is the meaning of h-index for journals, especially those recognized Journals?
The h-index for a journal is defined is just the same way that an h-index is defined for a person: the greatest value h for which there are at least h publications with at least h citations each.  Thus, for a journal, if it has published 1000 articles in its history, and 50 of them have received 50 or more citations, it would have an h-index of 50.