WordNet (r) 3.0 (2006):

MDI
    n 1: a Sunni organization formed in 1989 and based in Pakistan;
         opposes missionary groups from the United States; has
         Lashkar-e-Tayyiba as its armed wing [syn: Markaz-ud-Dawa-
         wal-Irshad, MDI]

The Free On-line Dictionary of Computing (19 January 2023):

Multiple Document Interface
MDI

    (MDI) The ability of an application program to
   show windows giving views of more than one document at a time.

   The opposite is Single Document Interface (SDI).

   (1999-03-30)