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'.
(..) ...than "being". Lucy. what did you do with my stomach? Nothing! Just a little horizontal slit. It's very well done and you'll find in a month, this scar is practically invisible. You'll be in shape for the beach next summer. I don't care about the scar. Is it, uh...is it why we opened you up? (..)2014 Lucy