VMS Help DEFINE, /KEY, Qualifiers, /TERMINATE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /TERMINATE
       /NOTERMINATE (default)

    Specifies whether the current equivalence string is to be
    processed immediately when the key is pressed (equivalent to
    entering the string and pressing Return). By default, you can
    press other keys before the definition is processed. This allows
    you to create key definitions that insert text into command
    lines, after prompts, or into other text that you are entering.