I think the word you're
looking for is... "INVISIBLE."
The Big Bang Theory Season 5, Episode 17
...and shouts, "Who wants
to take a ride in my INVISIBLE plane?"
The Big Bang Theory Season 4, Episode 5
He's just friends with
an INVISIBLE trumpet player?
The Big Bang Theory Season 11, Episode 17
that the Invisible Girl
is standing there with us.
The Big Bang Theory Season 7, Episode 14
The control system may be
INVISIBLE to us.
Westworld Season 2, Episode 10