hi-lock-mode-hook is a variable defined in `hi-lock.el'.
Its value is
(hi-lock-mode-set-explicitly)
This variable may be risky if used as a file-local variable.
Documentation:
Hook run after entering or leaving `hi-lock-mode'.
No problems result if this variable is not bound.
`add-hook' automatically binds it. (This is true for all hook variables.)