I have some code that defines the request variable req dynamically, so that instead of
(defop foo req
(pr (arg req "bar")))
I can say
(idefop foo
(pr (arg "bar")))
I found myself thinking in my own mind "OK, so here in this code I'm using req implicitly..."
Good names for concepts are always valuable, so paying attention to what my mind was calling this, I thought "Hmm, how about the name 'implicit variables'?"