The DEFINE command associates an equivalence string and a set of
  attributes with a key on the terminal keyboard. /KEY is required.
  For more information, see the DEFINE/KEY command in the OpenVMS
  DCL Dictionary. Control keys can be defined as follows:

  Format:  DEFINE/KEY key-name equivalence-string

  Example: DEFINE/KEY CTRLW "REFRESH"/TERMINATE

  The control-W key is defined by default as shown in the above example.
  For additional information on other default key definitions, see help
  on DEFAULT_KEYPAD.