Source : Free On-Line Dictionary of Computing

Run-Time Type Information
     
         (RTTI) Facilities included in {C++} {compilers} to
        allow the {type} of an object to be determined at {run time}.
     
        This facility, found in good C++ compilers and some other
        {high level languages}, adds type information to memory
        resident objects (i.e. type name or unique type-id).  This
        allows the {run-time system} to determine if an object is of a
        specific type, for example, to ensure that a {cast} of an
        object is valid.
     
        (1996-04-15)