Final answer:
The MeSH Database is used to identify the PubMed indexing language.
Step-by-step explanation:
The tool that is used to identify the PubMed indexing language is the MeSH Database. MeSH stands for Medical Subject Headings and it is a controlled vocabulary thesaurus created by the National Library of Medicine. MeSH terms are used to index the articles in PubMed and help researchers retrieve relevant information on a specific topic.