a letter written in 'invisible ink' [=ink that can only be seen when it is specially treated in some way]
It felt like I was 'invisible' at the party. [=no one was paying any attention to me at the party]
With the telescope we can see details of the planet's surface that are ordinarily 'invisible'.
(..) I mean, is it hard work? Yes. Duh. Like, that's the cliché, right? "Ah, it's so hard," because it is. You know, one second everything's great, and then you step on some invisible land mine, and you're fighting. Boom! Ka-boom! Uh... 'Cause it's hard. It's just... It's hard. (..)2017 TvShow: Superstore Title: Cheyenne's Wedding Season: 2 Episode 20