invisible-inkpen
nounUK /ɪnˈvɪzəbl ˈɪŋk pɛn/
US /ɪnˈvɪzəbl ˈɪŋk pɛn/
A pen that writes with ink you cannot see.
Maya used an invisible-inkpen to write a secret message to her friend.
OTHER MEANINGS
2. A pen whose marks only appear under special light.
The detective shined a UV light on the note made with an invisible-inkpen.
3. A toy pen that seems to write nothing at all.
For the magic trick, he scribbled with an invisible-inkpen and showed a blank page.
4. A pen used to hide words until they are revealed later.
She hid the answer with an invisible-inkpen so only her sister could find it.